Preheat the oven 400F.
Start by cooking your vegetables over medium heat in a little oil, maybe with a bit of chopped garlic or shallot.
Once everything is tender, add the beaten and seasoned eggs. (Note: the amount of the eggs depends on the size of your pan.) Sprinkle cheese on top.
Employ the edge-lift technique: gently lift up the set portions of your frittata, and let any egg mixture that is not set run into the space you've created. This will help everything to cook evenly.
As soon as the eggs begin to set over the stove, slide the whole thing into the oven briefly to finish cooking (remember, it will keep cooking in the hot pan after you pull it out). Wait until it's caramelized and toasty.