• Cut a small corner from the steak packaging and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel. Season generously with salt and pepper.

In a large sauce pot over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the steak and cook, stirring occasionally, until browned but not yet cooked through, 2 to 4 minutes. Transfer the steak to a plate. Do not clean the pot.
While the steak cooks, prepare the vegetables.

• Finely chop, press, or grate enough garlic to measure 1 teaspoon.
• Grate or peel and finely chop enough ginger to measure 1 teaspoon.
• Peel and thinly slice the yellow onion.
• Cut away any core from the cabbage; thinly slice the cabbage.
• Remove the stem, ribs, and seeds from the bell pepper; thinly slice the pepper.

In the same pot used for the steak, if dry, add 1 tablespoon oil and warm over medium heat until hot but not smoking. Stir in the garlic and ginger and cook until fragrant, about 1 minute. Add the onion and cook, stirring occasionally, until starting to soften, 2 to 3 minutes. Add the cabbage, bell pepper, and carrots and cook, stirring occasionally, until just softened, 4 to 6 minutes.

Add the steak and any accumulated juices to the pot. Stir in ¼ cup water and 1 tablespoon of the tamari and bring to a boil. Using tongs, place the udon on top of the stew; do not stir. Reduce to a simmer, cover, and cook until the udon are just tender, 4 to 6 minutes. Stir the udon into the stew. Season to taste with salt, pepper, and more tamari, if desired.
While the udon cooks, prepare the garnishes.

• Trim the root ends from the scallions; thinly slice the scallions on the diagonal.
• Coarsely chop the cilantro.

Transfer the beef and noodle stew to individual bowls. Garnish with the scallions and cilantro and serve.