When we travel by car, I make the frittata the night before, stuff it into pita bread in the morning and microwave for a minute or two before I wrap them in a towel so down the road we can enjoy a still-warm breakfast! —Carol Blumenberg, Lehigh Acres, Florida
Preheat oven to 350°. Whisk together eggs and salt.
In an 8-in. ovenproof skillet coated with cooking spray, heat oil over medium heat; saute onion and zucchini until onion is crisp-tender. Pour in egg mixture; cook until almost set, 5-6 minutes. Sprinkle with cheese.
Bake, uncovered, until cheese is melted, 4-5 minutes. If desired, sprinkle with pepper.