Preheat oven to 425 degrees. Place a wire rack inside of a jellyroll plan. Lay bacon slices over the wire rack. Cook bacon for 12 to 15 minutes in the oven.
Prepare the salad, place the spinach in a bowl, add tomatoes, chopped hard boiled eggs, and sliced red onion to the spinach.
After the bacon has cooked reserve 2 tablespoons of the bacon grease. Chop the bacon and place it on the salad.
In a saucepan add the bacon grease, red wine vinegar, sugar, and Dijon mustard. Turn the heat to medium and begin to whisk the salad dressing until it beings to bubble, and the salad dressing turns into a uniform salad dressing.
Pour hot bacon salad dressing over the spinach salad, mix the salad dressing into the salad.