Prep everything first: halve and pit the avocado and slice it into thin slices or dice it; finely dice the onion and mince the garlic; chop the cilantro; wash and pat-dry the lettuce leaves. Having everything ready speeds cooking and ensures the beef is served hot — and the dry lettuce holds fillings better than wet leaves.

Heat a medium nonstick or cast-iron skillet over medium-high heat for 1–2 minutes until hot. Add the olive oil and swirl to coat. Heating the pan before adding oil lets the oil thin and evenly coat the surface, preventing sticking and encouraging a good sear on the beef.

Add the diced onion to the hot oil and cook for 2–3 minutes until it becomes translucent and just starting to brown. Cook the onion first to soften it and draw out its sweetness, which balances the spices and beef.

Add the minced garlic and cook for 20–30 seconds until fragrant. Garlic burns quickly — short cooking releases its aroma without turning bitter.

Add the 6 oz (170 g) lean ground beef to the pan, breaking it up with a spatula. Spread it into an even layer and let it sit for 45–60 seconds before stirring: allowing some contact time helps develop brown bits (the Maillard reaction) that add deep umami flavor.

Sprinkle the cumin, chili powder and smoked paprika over the beef, and season with 1/4 tsp kosher salt and a few grinds of black pepper. Stir and continue to cook over medium-high heat until the beef is fully browned and any released liquid has evaporated, about 3–4 minutes more. Toasting the spices directly on the beef in the pan 'blooms' their oils and intensifies flavor.

Taste a small piece and adjust seasoning — add an extra pinch of salt if it tastes flat, or another 1/4 tsp chili powder if you want more warmth. Once seasoned to your liking, remove the pan from the heat and stir in half the chopped cilantro to keep its bright herbal flavor fresh.

Assemble the tacos: Arrange 3–4 lettuce leaves per person on a platter. Spoon 2–3 tablespoons of the warm spiced beef into each leaf (keep portions modest so the leaf holds). Top with diced or sliced avocado and about 1–2 tablespoons of salsa per taco. Using warm beef in cool crisp lettuce creates a pleasant hot-cold contrast — a hallmark of great tacos.

Garnish with remaining cilantro and serve immediately with lime wedges for squeezing over the tacos. A squeeze of lime brightens the dish and balances the richness of the beef and avocado.

Optional final flourish: if you like a little heat, add a few drops of hot sauce or thinly sliced fresh jalapeño on each taco. Serve immediately so the lettuce stays crisp.