Step 1
Preheat the oven to 350 degrees F (175 degrees C).
Step 2
Season the skinless side of the turkey breast with 1/2 of the kosher salt and herbes de Provence. Season the skin side with the remaining kosher salt. Place turkey skin-side up into an oiled baking dish.
Step 3
Roast in the preheated oven until an instant-read thermometer inserted into the turkey registers 148 degrees F (64 degrees C) 45 to 60 minutes.
Step 4
Place bacon on a baking sheet lined with aluminum foil. Remove turkey from the oven and let cool.
Step 5
Bake bacon in the hot oven until about halfway cooked 10 to 15 minutes.
Step 6
Melt butter in a pot over medium heat. Stir in flour until combined. Cook stirring occasionally until roux smells like cooked pie crust about 3 minutes. Whisk in cream all at once. Cook until Mornay sauce is thickened and starting to boil about 5 minutes. Immediately turn off the heat.
Step 7
Season Mornay sauce with salt black pepper and cayenne pepper. Stir in 1/2 cup Pecorino Romano cheese until combined. Add nutmeg and stir briefly.
Step 8
Cut turkey into thick slices. Pull off the skin.
Step 9
Stack 2 bread slices on top of each other and trim off the crusts. Cut 1 slice into 2 triangles. Place bread in a small baking dish set on top of a sheet pan. Top bread with 3 slices of turkey. Place 3 tomato slices in between. Ladle 1/4 of the Mornay sauce all over and cover with 2 tablespoons Pecorino Romano cheese. Sprinkle with paprika; lay the partially cooked bacon across the top. Repeat with remaining ingredients to make 3 more servings.
Step 9
Set an oven rack about 6 inches from the heat source and preheat the oven's broiler.