Using a sharp knife, pierce each quail through the breastbone, and flatten out the bird with the palm of your hand. Score down both sides of the spine and remove the backbone.
Add the sesame seeds, cumin and 2 teaspoons sea salt to a small frying pan over medium heat. Toast the spiced salt mixture, stirring frequently, until the sesame seeds are fragrant, about 1 to 2 minutes.
Preheat a barbecue grill plate to high heat.
Brush each quail evenly with the olive oil and season with salt and pepper, to taste. Grill the quail, skin side down, until the outside is crisp and the interior is cooked through, about 5 minutes per side. Sprinkle each quail with a dash of the spiced salt and a squeeze of lemon juice.