Warm the skillet: Heat a large nonstick or cast-iron skillet over medium heat.
Add the olive oil and swirl to coat.
Sauté aromatics: Add the onion and red bell pepper. Cook, stirring occasionally, until softened, about 5 minutes. Stir in the garlic and cook 30 seconds, until fragrant.
Brown the beef: Add the ground beef.
Break it up with a spatula and cook until no longer pink, 5–7 minutes. Spoon off any excess grease if needed.
Season boldly: Sprinkle in chili powder, cumin, smoked paprika, oregano, red pepper flakes (if using), salt, and black pepper. Stir to coat the meat and vegetables evenly.
Add veggies and beans: Stir in zucchini, tomatoes, and black beans.
Pour in the broth. Mix well, scraping up any browned bits from the bottom of the pan.
Simmer to meld flavors: Reduce heat to medium-low. Let the mixture simmer, uncovered, for 5–7 minutes, until the zucchini is tender and most of the liquid has reduced.
Finish with freshness: Squeeze in the lime juice and fold in the cilantro.
Taste and adjust salt and pepper as needed.
Serve your way: Spoon into bowls over rice or quinoa, tuck into tortillas, or serve with a side of shredded lettuce and avocado. Add your favorite toppings.