Protein-rich eggs and fresh, seasonal vegetables are the secret to this healthy frittata. Well-known in the Mediterranean diet, the frittata can be enriched with any seasonal vegetables and cheeses to create your own personal recipe. This one features year around summer squash, a good source of vitamin C along with some fiber and potassium.
Coat pan heavily with cooking spray and set over medium-high heat. Sauté onion until golden, 3-4 minutes. Mix in garlic and cook 1-2 minutes, until onion is lightly browned. Transfer contents of pan to plate to cool.
Coat pan again with cooking spray and return to heat. Add zucchini and cook until slices look moist and translucent. Using tongs, keep spreading and turning zucchini to brown slices on both sides, 8-10 minutes, adding to onion mixture as zucchini slices brown. Wipe out the pan.
In mixing bowl, whisk eggs and whites until well combined. Mix in cheese, salt and pepper. Add vegetables and basil, and mix with fork to combine with eggs.
Add oil to pan and tilt pan to swirl oil around sides. Set pan over medium-high heat. Pour in egg mixture, spreading zucchini and onion in an even layer. As eggs start to set, use wide spatula to lift frittata around edges while tilting pan slightly so liquid egg flows out and under the edges. Cook until frittata is browned on bottom and set except in center, about 8 minutes. Off heat, invert large plate over pan. Pressing it firmly in place against the pan, invert the two so frittata falls from pan onto plate. Slide frittata back into pan and cook to lightly brown bottom, 1-2 minutes longer. Slide frittata onto serving plate. Serve immediately, or cool frittata to room temperature before serving. This frittata also can be covered and refrigerated overnight. Cut into 4 wedges, and serve.