Grate the red onion over a bowl, transfer to a sieve and press to extract excess water. Discard onion water.
Transfer grated onion to a large bowl along with the lamb, garlic, oregano, mint, cumin, coriander, breadcrumbs, egg, oil, cheese, salt and pepper. Mix using your hands and squeeze mixture until thoroughly mixed.
Set up small bowl with flour. Shape meat mixture into walnut size meatballs (See Note 2) and roll in the flour to coat. Gently shake excess flour off and place on a tray. Repeat and you should end up with 36 meatballs.
Fried Version
Heat 1/2-inch of olive oil in a deep skillet until it just starts to shimmer. Fry the meatballs for 7 minutes and brown all over in several batches. Remove and keep warm on a paper towel lined plate.
Baked Version
Bake in 400°F oven for 20 minutes on parchment lined, rimmed baking sheet.
A traditional Greek kefalotyri cheese is preferred if you can find it.
After rolling the meatballs and before rolling in the flour, I often times save half the batch to freeze. Later, when ready to use, thaw and dredge in flour before frying.
You could also bake these on a tray after dredging in the flour in a 400°F oven for 18-20 minutes if you do not want to fry. They will not be as crispy though.