Preheat your oven to 375°F. Set a large pot of water on the stove, add a dash of salt and a drizzle of olive oil to it, and bring it to a boil. Once boiling, add pasta and cook according to package instructions (I recommend slightly al dente), then drain and set aside.

In another large pot, melt butter. Once melted, add flour and stir until combined and thickened into a roux (paste-like mixture).

Slowly add milk while whisking, until the mixture is creamy, thick, and smooth.

Remove from the heat and add in sharp cheddar cheese and Gruyere cheese, stirring until melted, well-combined, and smooth.

Add salt and pepper to taste.

Mix the cooked pasta into the cheese sauce. Spray a 9 by 13-inch baking dish with cooking spray, then add the macaroni and cheese to the dish, smoothing it into an even layer.

Melt the remaining butter in a medium saute pan over medium heat. Add breadcrumbs and cook until golden, stirring constantly to avoid burning. Remove from the pan immediately once browned.

Place tomato slices in an even layer over the top of the macaroni and cheese in the baking dish (optional).

Sprinkle the breadcrumbs over the top.

Bake for 30 minutes, until bubbling and edges begin to brown. Serve, and enjoy!