Season the Beef:

Place the beef strips in a bowl and sprinkle with garlic powder, kosher salt, and black pepper. Toss to ensure even coating.

Sear the Beef:

Heat the oil in a large skillet over medium-high heat.

Add the seasoned beef and sear on all sides until lightly browned (about 5 minutes). The beef does not need to be fully cooked at this point.

Transfer the browned beef along with any juices to a 6-quart slow cooker.

Sauté the Onions:

In the same skillet, add the sliced onion.

Increase the heat to high and pour in ¼ cup water to deglaze the pan, scraping up any browned bits.

Sauté the onions until they begin to soften and turn lightly brown (around 3 minutes), then add them to the slow cooker.

Assemble the Slow Cooker:

Add the green and red bell peppers and the can of fire-roasted diced tomatoes (with their juices) to the slow cooker.

Prepare the Sauce:

In a small bowl or large measuring cup, whisk together:

¼ cup low sodium soy sauce

2 tablespoons Worcestershire sauce

2 tablespoons honey

1 tablespoon minced fresh ginger

¼ teaspoon red pepper flakes

3 tablespoons cornstarch

Pour the sauce mixture over the ingredients in the slow cooker.

Slow Cook:

Cover and cook on LOW for 6 to 7 hours, until the beef is tender. (Alternatively, cook on HIGH for 3 to 4 hours if needed, though the beef may be slightly less tender.)

Thicken the Gravy:

In a small bowl, mix the remaining 2 tablespoons cornstarch with 2 tablespoons water to create a slurry.

Stir the slurry into the slow cooker.

Switch the slow cooker to HIGH and cook uncovered for an additional 10 minutes, allowing the sauce to thicken into a rich, velvety gravy.

Final Seasoning & Serve:

Give the dish a final stir and taste. Adjust the seasoning with extra salt, soy sauce, or red pepper flakes if desired.

Serve hot over your choice of brown rice, quinoa, or cauliflower rice.

Garnish with a sprinkle of green onion, if desired.