In a small (8-in) skillet with a lid, saute onion in olive oil until translucent. Add garlic and arugula and stir to mix in the onion (the arugula will wilt, but it does not need to cook down).
Pour the eggs over the arugula in the pan. Scatter goat cheese over top of the eggs. Turn heat to low, cover, and cook until the egg is set, about 4-5 minutes.
Recipe by Alisons Allspice at https://www.alisonsallspice.com/arugula-goat-cheese-frittata/