Preheat the oven to 350 degrees Fahrenheit. Spray a 9 x 13 inch baking dish with cooking spray.

In a large pot of boiling salted water, cook the pasta according to package instructions until al dente and drain well.

Meanwhile, in a large skillet, heat the olive oil over medium-low heat. Add the onions and cook until soft, about 5 minutes. Stir in the garlic and cook for 30 seconds.

Add the ground beef to the skillet, cook until browned, and season with salt and pepper.

Stir in the tomato paste, diced tomatoes, and Dijon mustard. Let simmer until mixture slightly thickens, about 2 minutes.

Combine the cooked pasta with the meat mixture and spread into the prepared baking dish.

Top with grated cheddar cheese and bake until cheese melts, about 15 minutes. Sprinkle chopped dill pickles over the top and serve.