Preheat the oven to 350˚F. Lightly spray a 9x13 inch baking dish with cooking spray and set aside.
In a large saucepan, bring salted water to a boil. Cook the elbow pasta according to package instructions. Drain and set aside.
Meanwhile, heat the oil in a medium skillet over medium heat. Add in the onion and cook until fragrant. Stir in the garlic and cook for an additional minute.
Mix in the ground beef and cook until no longer pink. Season with salt and pepper.
Mix in the tomato paste, diced tomatoes and mustard powder. Cook until the mixture thickens a little more, around 2 minutes.
Add in the pasta and mix until fully incorporated. Mix in 1 cup of cheese.
Pour the mixture into the prepared baking dish. Top with the remaining cheese and bake in the preheated oven for 15 minutes, or until the cheese is melted.
Top with the pickles and enjoy!