Preheat the oven to 400F and position the top rack in the middle of the oven.
In a medium bowl, combine the ricotta, Mozzarella, and Parmesan cheeses, and set aside.
Cook the filling:
Heat a large skillet over medium-high heat. Once hot, add the oil and spread it over the pan. Cook the ground beef on the hot pan, breaking it up with a spatula as you go. As the meat is cooking, add the garlic powder, Italian seasoning, and salt to the pan. Stir to distribute seasonings and continue cooking the ground beef until it's cooked through. Turn off the heat and set aside.
While the meat cooks, spray the muffin pan with oil. Place one wonton wrapper inside each cup, gently pushing them down into the space.
Assemble & Bake:
Fill each cup with 1 tablespoon of ground beef, top it with 1 tablespoon of marinara sauce.
Top this first layer with another wonton wrapper by placing it on top of the sauce, gently shaping it into the cup shape. Spoon another tablespoon of the cooked meat, another tablespoon of marinara, and one tablespoon of the cheese mixture at the very top. Use the back of the spoon to gently press it down into the cupcake shape.
Bake in the preheated oven for 10 to 15 minutes, until the edges are golden brown and crispy and the cheese on top has melted. Remove from the oven.
Serve:
Carefully remove each lasagna cup from the muffin pan onto a serving plate or board, using a rounded knife if necessary to help lift them out.