Cook the elbow macaroni according to package instructions until al dente. Drain and set aside.

In a large skillet or Dutch oven, cook the ground beef and onion over medium-high heat until browned and cooked through. Drain any excess grease.

Add the garlic powder, salt, diced tomatoes and green chilies, condensed cream of mushroom soup, and milk to the skillet and stir everything together.

Add the cubed Velveeta cheese to the skillet and stir everything together until the cheese is melted and smooth.

Add the cooked elbow macaroni to the skillet and stir everything together until the macaroni is coated in the cheese sauce.

Let the mixture simmer on low heat for a few minutes, stirring occasionally, until heated through.