1 tbsp. extra-virgin olive oil
3/4 lb. ground beef
1 medium onion, chopped
1 (1-oz.) packet taco seasoning
4 large, ripe beefsteak tomatoes
1/2 c. shredded Mexican cheese blend
1/2 c. shredded iceberg lettuce
1/4 c. sour cream
In a large skillet over medium heat, heat oil. Add onion and cook, stirring, until soft, 5 minutes. Add ground beef and taco seasoning. Cook, breaking up meat with a wooden spoon, until no longer pink, 8 minutes. Drain fat.
Flip over tomatoes so they’re stem-side down and slice to make 6 wedges, being careful not to cut all the way through. Carefully spread open wedges.
Divide taco meat among tomatoes, then top each with cheese, lettuce, and sour cream before serving.