Whisk the eggs with salt, black pepper, and the grated Parmesan cheese. Do not over-whisk, as too much air will cause the frittata to collapse later.
Slice the tomato and place the slices on paper towels for a moment to drain the excess moisture. Tear the mozzarella into large pieces and let them drain as well; wet cheese will make the center of your frittata watery.
Heat the olive oil in a small skillet over medium heat and pour in the egg mixture. Let it set for two minutes without stirring, then distribute the tomato and mozzarella over the surface and turn the heat down to low.
Cover the pan and let the frittata cook gently for six to eight minutes until the top is just set and the cheese has melted. Slide it onto a plate, tear fresh basil over it, and grind some black pepper on top. Three eggs with cheese provide over twenty grams of protein and virtually no carbohydrates.