Preheat oven to 350 degrees.

In a large bowl, whisk together the eggs and a few rinds of black pepper; set aside.

Warm a 10- to 11- inch oven-proof sauté or cast iron pan over medium high heat. Add the bacon and fry until crispy. Remove bacon and set aside, leaving bacon fat in the pan.

In the same pan, warm the bacon fat over medium heat and add the onion. Sauté the onions for about 2 minutes until softened and lightly browned. Add the garlic, cherry tomatoes and spinach leaves and stir.

Add the whisked eggs and let set for about 30 seconds over medium heat.

Transfer the pan to the preheated oven and let the frittata cook until the eggs are just set, about 25-30 minutes. Remove the frittata from the oven, cut into wedges and serve.