Start this off by preheating your oven to 350 degrees Fahrenheit. Be sure to wash your Swiss chard 3 or 4 times under cold clean water to remove any dirt and remove the stems. The stems can still be cooked but these should be sliced into thin strips, however, the leaves need to be chopped in course bits. Your onion needs to be sliced into thin slices that are ¼ thick.
Add one or two tablespoons of olive oil into your skillet, add your onion, and stir this for 5 minutes to cook them. When this is done, you can now add your chard and stems while adding salt and pepper for taste and cook for another 5 minutes, until the leaves are tender.
Remove any liquid from the skillet by using a flat lid that fits inside and squeeze out anything remaining. You can now crack your eggs into a large bowl using salt and pepper and a simple pinch of cayenne chili powder and 2 cloves of your chopped garlic. Use a metal whisk to get plenty of air into this egg mixture.
Add the chard and onion mix from your skillet and mix this into the egg mix. This gives you a chance to wipe out your skillet with a paper towel to remove any remaining liquids. Now you can add another 2 tablespoons of olive oil into the skillet on medium heat and pour your egg mixture that has the chard and onions mixed in.
Allow this mixture to cook on the stovetop for 2 or 3 minutes to get the egg to cook along the edges and bottom of the pan. After this, remove the skillet into the oven and cook for an additional 8-10 minutes. This will help cook and set the rest of the eggs
After the eggs are cooked, remove the skillet using an oven mitt or kitchen towel so you don’t get burned. Place the skillet onto a cutting board and take a pairing knife to release the edges of your frittatas. Place a plate onto the very top and carefully flip the frittatas upside down. Use another plate to flip it back again.
Now you can slice and serve your frittatas into 4 equal slices or 8 slices to make smaller servings. Enjoy!