Spray a 9x13-inch baking dish with nonstick cooking spray. Set aside.

Finely dice the onion. Set aside.

Finely chop the bacon. Set aside.

Preheat the oven to 375°F.

Set a large saute pan over medium-high heat. Add the bacon and cook until browned and crispy.

Use a slotted spoon or spatula to transfer the bacon pieces to the paper towel-lined plate. Remove all but 1 tablespoon of bacon fat from the pan, then return the pan to the stove.

Add the elbow macaroni to the pot of boiling water. Cook, stirring occasionally, until the pasta is al dente, 9-10 minutes. Drain the pasta in a large colander, and rinse thoroughly with cold water.

Add the diced onion to the pan used to cook the bacon. Saute until translucent, 5-6 minutes.

Add the ground beef to the pan with the onions. Cook until browned, 4-5 minutes.

Reduce the heat to medium. Add the garlic powder, ketchup, yellow mustard, salt, and black pepper. Stir to combine.

Add the bacon to the beef mixture and continue to cook for 1 minute. Remove the pan from the heat, and set aside.

In a large pot over medium heat, melt the butter.

Once melted, add the flour. Whisk to thoroughly combine. Continue whisking until the roux turns slightly golden and begins to smell toasty, 1-2 minutes.

Slowly stream the milk into the pot while continuing to whisk. Cook the mixture, whisking steadily, until it begins to thicken and bubble, 4-5 minutes.

Once bubbling, turn off the heat. Add the ground mustard, garlic powder, salt, and pepper.

Add the cheeses to the pot a handful at a time, whisking slowly after each addition.

Once the sauce is smooth, add the drained pasta noodles and beef mixture to the pot. Stir until combined.

Pour the pasta into the prepared baking dish.

Bake the mac and cheese on middle rack of oven until bubbling at the edges, 25-28 minutes.

Check to see that mac and cheese is done. Remove from oven or add time as needed.

Allow mac and cheese to rest for 15-20 minutes before serving. Serve with ketchup, if desired.