Core tomato and cut into ¼" dice.
Mince cilantro (no need to stem).
Stem jalapeño, halve, seed, remove ribs, and mince. Be sure to wash hands, utensils, and cutting board after working with jalapeño.
Halve and peel onion. Slice halves into thin strips.
Hold romaine heart at root end and slice thinly.
Make the Pico
Combine tomato, cilantro, jalapeño (to taste), ¼ tsp. salt, and a pinch of pepper in a mixing bowl.
Cook the Beef
Place a medium non-stick pan or cast iron skillet over medium heat and add 1 tsp. olive oil.
Add ground beef to hot pan and stir occasionally until lightly browned, 2-3 minutes.
Add onion and stir occasionally until tender, 3-5 minutes.
Stir in seasoning, ¼ cup water, ½ tsp. salt, and a pinch of pepper. Stir until thoroughly combined, 1 minute.
Melt the Cheese
Top beef with cheese and let melt, 1 minute.
Remove from burner.
Finish the Dish
Serve family-style, with romaine as the base, topping with pico, romaine, sour cream, and tortilla strips. Bon appétit!