Season the beef cubes generously with salt, pepper, cumin, chili powder, and garlic powder; let the coating sit for 1 minute while you heat the pot. Aim for an even, dark spice layer on all sides (no bare spots).

Heat vegetable oil in a heavy pot over high heat, then brown the beef in batches without crowding for 2–4 minutes per batch, turning as needed. Cook until deep brown crust forms and juices look mostly reduced, then remove and set aside.

In the same pot, sauté the onion and green bell pepper for 5 minutes over medium-high heat. Stir until the vegetables soften and turn glossy.

Add the garlic and cook for 1 minute over medium-high heat, stirring to prevent scorching. It should smell fragrant but not dark.

Sprinkle the flour over the vegetables and stir for 1 minute. The mixture should look slightly thickened and smell toasty.

Add the beef broth and diced tomatoes, scraping up the browned bits from the bottom of the pot. Stir until smooth and bubbling.

Return the browned beef to the pot, add oregano, cover, and simmer on low for 1.5–2 hours until the beef is extremely tender and the gravy thickens. Keep the lid on and stir once or twice so the bottom doesn’t stick.

Warm the flour tortillas just before serving, then ladle the carne guisada into tortillas. The beef should look pull-apart tender and the gravy should cling to the chunks.

Top with cilantro and serve with fresh lime. Finish with bright lime over the top for a fresh, citrusy edge.