For the topping:
6-8 slices center-cut bacon (if you do not use center-cut bacon make sure to drain off some of the fat), chopped
1 medium yellow or sweet onion, chopped
1/2 cup bread or panko crumbs
For the macaroni and cheese:
1 7-ounce package elbow macaroni
1/4 cup unsalted butter, cubed
1/4 cup all-purpose flour
1/2 teaspoon salt
1/4 teaspoon pepper
1/2 teaspoon paprika
1/2 teaspoon Coleman's dry mustard (optional)
2 cups whole milk
8 ounces white cheddar cheese, shredded
1 large, ripe tomato, seeded and chopped
Preheat your oven to 250 F.
Make the breadcrumb topping: In an oven-proof pan, sauté bacon on medium-high until bacon is crispy, about 6-7 minutes. Remove bacon with a slotted spoon and set aside. Add onion to the pan and sauté in bacon fat until beginning to brown, about 5-6 minutes. Add breadcrumbs to pan and sauté until crumbs are toasted and crispy. Remove the mixture from heat, add the bacon back in and stir gently to combine. Put your pan in the oven to keep topping warm while you make the mac and cheese.
Next, cook macaroni according to package directions. Meanwhile, in a large saucepan, melt butter over medium heat. Stir in flour, salt, pepper, paprika and mustard (if using) until smooth; gradually whisk in milk. Bring to a boil, stirring constantly; cook and stir 1-2 minutes longer or until thickened.
Stir in cheese until melted. Drain macaroni; add to cheese sauce and stir to coat. Put macaroni and cheese in individual serving bowls, top with tomato and some of the breadcrumb topping. Serve right away.