Preheat the oven to 375.

Drizzle oil into a pot of boiling/salted water.

Mix in the macaroni and cook according to the directions on the package (6 to 8 minutes).

Drain well.

Heat the milk in a small saucepan, careful not to boil it.

Melt 6six tablespoons of butter in a four-quart pot and add the flour.

Cook over low heat for about two minutes, stirring with a whisk.

At the same time, mix in the hot milk and cook for a minute or two more, until thickened and smooth.

Off the heat, toss in the Gruyere, Cheddar, one tablespoon salt, pepper, and nutmeg.

Add the cooked macaroni and stir well.

Pour into a three-quart baking dish.

Slice the tomatoes and arrange on top.

Melt remaining two tablespoons of butter and combine them with the fresh bread crumbs; sprinkle on the top.

Bake for 30 to 35 minutes, or until the sauce is bubbly and the macaroni is browned on the top.