Bring a large pot of salted water to a boil. Add the whole wheat pasta, and cook until al dente. 

While the pasta is cooking, add ground beef to a large skillet pan. Season beef with the garlic powder, cayenne pepper, salt, and pepper and cook over medium-high heat. When beef is almost done cooking, add the ½ diced onion, reserving a tbsp to top the pasta at the end of cooking. Cook onion until slightly transparent, and ground beef is browned. While the beef is cooking, dice the roma tomatoes, and set aside. 

Drain the pasta, and add to the ground beef skillet. Reduce heat to simmer. 

Cut the velveeta cheese into large cubes, and add to the pot used to cook the pasta. Pour the heavy whipping cream over the cheese cubes, and cook over medium heat, stirring constantly. The whipping cream scorches easily, so it’s important to continuously stir. Once the cheese sauce is completely melted, pour over the pasta and ground beef in the large skillet pan. Stir well to mix all ingredients together. 

Add the roma tomatoes to the skillet, reserving two tablespoons. Gently mix the tomatoes into the pasta, just enough to incorporate. Top the pasta with the reserved onions and tomatoes, and serve.