Whisk the eggs, salt and black pepper vigorously in a mixing bowl, in order to beat a lot of air into the eggs to create a fluffier texture for the frittata. Then gently mix in the cubed tomato and parmesan cheese. Set aside.

Grease the bottom and sides of an 8-inch, oven-proof skillet with olive oil and heat over medium-high heat. Once hot, add a bit more olive oil to the pan and toss in the sliced yellow onion. Sauté for 5 minutes until the onion softens. Then add in spinach, and sauté for a quick minute, just until the spinach leaves start to wilt.

Turn heat down to medium-low, and add the egg mixture into skillet. As the frittata cooks, use a rubber spatula to gently lift the cooked edges to allow uncooked eggs to run down to the bottom of the skillet.

Once the eggs begin to set around the edges – after about five minutes - arrange the tomato slices on top (you can also add another layer of cheese, if desired).

Lower the heat to low, cover the skillet, and continue cooking for another 5-8 minutes.  As it cooks, occasionally shake the skillet gently to ensure it cooks evenly, and also remove the cover a few times and use a spatula to lift the frittata to prevent it from sticking to the bottom of the pan.

When the eggs are just about set (the top will be slightly runny) turn the fire off, uncover, and sprinkle on smoked Spanish paprika and chopped fresh herbs.

Turn the oven to broil and place the whole skillet into the oven. Broil for a few minutes (about 3-4 minutes), watch closely until the frittata is lightly browned and fluffy.

Remove from oven and loosen the frittata by gently shaking the pan. Cut into wedges and serve immediately.