Heat 2 tablespoons of olive oil in a medium nonstick skillet over medium heat. When the pan is hot, add in the onions and cook until translucent, about 6 minutes. Transfer to a plate and return the pan to the heat.
Step 2
Cook the zucchini over medium heat until softened and just beginning to get brown, about 5 minutes.
Step 3
While the zucchini is cooking, vigorously whisk the eggs in a large bowl until homogenous looking and slightly foamy. Add the grated parmigiano reggiano and stir until well combined.
Step 4
Stir the onions and zucchini to the egg and cheese mixture until evenly combined. With the heat on medium-low pour in the egg mixture and give the pan a gentle shake to settle the mixture.
Step 5
Cook the eggs until set around the edges and the sides, about 5 to 7 minutes. The center will still be slightly runny. Take a flat plate and place it over the top of the pan. Very carefully and holding firmly, flip the pan so that the frittata releases from the skillet onto the plate. Then carefully and quickly, slide the frittata back into the pan, cooked side up. Some of the runny eggs will be left on the plate but that is okay as most will have made it back into the skillet.
Step 6
Cook the frittata for an additional 3 to 5 minutes, until fully set. Slide the frittata out of the skillet and onto a plate to serve.
