Preheat your broiler. Crack the eggs and whisk them together with the almond milk in a bowl. Season lightly with salt and pepper, add 3-4 tbsp tomato sauce and Italian seasoning (if using), and whisk together again.
Slice the bell pepper. In a medium skillet, heat the oil over medium heat. Add the bell pepper and saute in the oil for 2-3 minutes.
Pour the egg mixture into the skillet, and gently pull the eggs away from the sides with the spatula, allowing the mixture to fill in. Do this a few times until it stops filling in quickly.
Lower the heat, then cover and cook together for about 4-5 minutes, until cooked through in the middle.
Uncover the eggs. If you're using mozzarella cheese, sprinkle it on top. Arrange the pepperoni on top. Place the skillet under the broiler to crisp up the pepperoni a bit.
Slide the frittata out of the pan onto.a cutting board, then drizzle with the remaining sauce. Season lightly with salt and pepper and sprinkle with fresh basil leaves, then slice and enjoy!
Calories do not include any added mozzarella cheese. I've heard that finding Whole30 compliant pepperoni is hard for a lot of people. If you cannot find Whole30 compliant pepperoni, dice up Chomps Turkey Pepperoni (use code COOKATHOME for a discount), or substitute a compliant prosciutto or salami.