Sheet Pan Greek Lamb Meatballs with Lemony-Yogurt Sauce

Preheat oven to 425 degrees.
Using a box grater, grate the onion over a large bowl.
To the grated onion, add the egg, 1 tablespoon of olive oil, grated or finely minced garlic, cumin, coriander, red chili flakes, kosher salt, black pepper, and panko breadcrumbs and mix well with a fork.
Next add the lamb and the parsley, mint and dill to the onion mixture and mix with your hands, just until the mixture comes together. Be careful not to over mix, otherwise the meatballs can become tough.
Using a large cookie scoop or a large spoon, scoop the meatballs and place them onto a sheet pan - don’t roll them yet!
Pick up each meatball and and make an indentation with your finger and place some feta inside. Cover up the feta and roll the meatball and then place it back on the sheet pan. Repeat this process with the rest of the meatballs.
Using the remaining tablespoon of olive oil, carefully brush the outside of the meatballs.
Roast the meatballs in the oven for 15 minutes. *If you scooped larger meatballs, they will require a longer bake time.
While the meatballs are roasting, add the yogurt to a small bowl and add the zest of the whole lemon and the juice of only half of the lemon, salt and pepper, and mix well. If the sauce is really thick, you can thin with water as you wish.