In a large bowl, whisk together the eggs, grated Parmesan cheese, salt, and pepper to taste. Set aside.
Heat the olive oil in a non-stick, oven-safe skillet over medium heat. Add the bacon and cook until it's crisp, then transfer it to a plate, leaving the bacon grease in the skillet.
Add the diced onion to the skillet and cook until tender. Then, add the sage and cook for 1-2 minutes, until fragrant.
Stir in the halved cherry tomatoes, cooked bacon, and egg mixture, ensuring everything is evenly distributed in the skillet.
Place the skillet in the preheated oven and bake for 15-20 minutes, or until the frittata is set and golden on top.
Remove the frittata from the oven and allow it to rest for a few minutes before serving. Cut into wedges and enjoy your Italian Sage and Bacon Frittata!
