Preheat your oven to 400°F and spray a 12-cup muffin tin with cooking spray.
In a large skillet, heat olive oil over medium heat, sauté diced onions until tender. Add ground beef and seasonings, cook until beef is browned (about 3-4 minutes).
Add drained tomatoes, stir until the liquid is mostly absorbed (about 5-7 minutes).
Assemble the cups with one wonton wrapper, cheese, another wonton, ground beef mixture, and remaining cheese.
Bake for 13-17 minutes until crispy, checking around the 10-minute mark.