Here's what separates mediocre beef from restaurant-quality beef: the marination period. Start this step first, even before you gather other ingredients. In a large mixing bowl, combine your sliced flank steak with 3 tablespoons water, 3 teaspoons cornstarch, the baking soda, 3 teaspoons neutral oil, and 6 teaspoons oyster sauce. Mix thoroughly—your goal is to coat every piece evenly. The baking soda will make the surface slightly tacky; this is perfect. Set this aside for at least 30 minutes, though 60 minutes is ideal. During this time, the proteins will relax, the starches will hydrate, and the beef will become incredibly tender when cooked. This is not a step to skip. While you wait, prepare everything else.

In a separate small bowl, whisk together 6 tablespoons soy sauce, 3 teaspoons sugar, 1½ teaspoons sesame oil, and ¼ teaspoon white pepper. This is your flavor foundation. Set it aside. By preparing this early, you're eliminating decision-making during the actual cooking phase, when speed and focus matter most.

Slice your 6 shallots into thin rings. Mince your garlic finely—3 cloves is subtle enough not to overwhelm but potent enough to carry through the week. Slice your ginger into clean, thin pieces. Cut your scallions on the bias, separating white parts from green parts into two piles. Cut your tomatoes into bite-sized wedges—they'll shrink slightly during cooking, so overshooting slightly is fine. Line everything up in small bowls in the order you'll use it. This is called mise en place, and it's the difference between calm, controlled cooking and chaos. You'll thank yourself when the wok is hot and you need everything instantly.

Heat your wok or large skillet over high heat until a drop of water immediately sizzles and evaporates—this should take 2-3 minutes. Add 3 tablespoons of neutral oil and let it get just barely smoking. Your beef has been marinating and is ready. Working in two batches (this is crucial—crowding the wok drops temperature and creates steam instead of sear), spread half your beef around the wok in a single layer. Resist the urge to stir for the first minute. You want a golden crust to form. After 60 seconds, toss everything for another 20 seconds until the beef is about 80% cooked through—it will finish cooking when you add it back later. The internal temperature should read about 130°F on an instant-read thermometer. Transfer the first batch to a clean plate and repeat with the remaining beef. This entire process takes roughly 3 minutes total. Set both batches aside on the same plate—the beef juices pooling together will enrich your final sauce.

Add your remaining 3 tablespoons of oil to the wok over medium heat. Add your ginger slices and let them caramelize undisturbed for about 10 seconds—you're not cooking the ginger, you're blooming its essential oils into the oil. Turn heat to high, then immediately add your minced garlic, shallots, and the white parts of your scallions. Toss this combination for exactly 10 seconds. The aromatics should soften but not brown. This is quick, intentional cooking. Next, add your 6 tablespoons of ketchup and fry for 30 seconds. The ketchup will caramelize slightly and become deeply fragrant—this is your cue that the base is ready.

Add all your tomato wedges to the wok in an even layer. Resist stirring for the first 15 seconds—let them make contact with the hot surface. This creates a slight char and deepens the tomato flavor. Then add your 3 tablespoons of Shaoxing wine, and toss everything together for another 10 seconds. The alcohol will almost entirely cook off, leaving only its complex, slightly sweet depth. Now push all your tomato-aromatic mixture to one side of your wok, creating a clear space on the other side. Add your reserved sauce base (soy sauce, sugar, sesame oil, white pepper) to the clear space and let it bubble for just a few seconds. This blooming process melds the flavors together rather than having them remain distinct.

Add your seared beef and all its accumulated juices back to the wok. Toss everything together on high heat for about 20 seconds—you're combining textures and ensuring every piece is coated in sauce. The beef will finish cooking through, and the tomatoes will begin to break down slightly, thickening the sauce naturally. Do not walk away during this step. This is the moment where beef-tomato moves from "good" to "exceptional." The residual heat from the beef finishes cooking through while the tomato sauce hugs every surface.

Add the green parts of your scallions to the wok. Now, slowly add your cornstarch slurry (3 tablespoons cornstarch mixed with 3 tablespoons water) while stirring. Add it gradually—you may not need all of it. Stop when the sauce reaches your preferred consistency. It should coat the back of a spoon but still flow slightly. Let it cook for 15 seconds after the final addition to ensure the cornstarch is fully activated and the raw starch taste is gone. Taste it. Adjust salt or sugar if needed. Remember: this will be eaten across five days, and flavors will concentrate slightly during storage, so season conservatively.

Move your finished beef-tomato to your prepared storage containers while it's still steaming hot. Hot food transfers more effectively into containers, and the residual heat will help preserve the dish during initial cooling. Let containers cool to room temperature (about 30 minutes) before sealing and refrigerating.