Preheat broiler to high; position oven rack in top third of oven. Line a baking sheet with aluminum foil and lightly spray with cooking spray.
Heat 2 tablespoons of olive oil in a medium saucepan over medium heat. Add garlic and sauté 30 seconds until fragrant.
Add tomato puree, Italian seasoning, and salt and gently simmer for about 20 minutes or until sauce is thickened. Remove from heat.
Arrange eggplant slices in a single layer on prepared baking sheet. Brush with olive oil, then season with salt and pepper. Flip and repeat with other side.
Broil eggplant for 4 to 5 minutes per side, until softened and starting to brown.
Set oven temperature to 350 degrees F.
Spread a spoonful of sauce into the bottom of each ramekin. Top with a slice of eggplant, followed by another spoonful of sauce, sprinkle with Italian seasoning, then an even coating of mozzarella cheese and a bit of Parmesan cheese.
Repeat, layering two more slices of eggplant with sauce, sprinkle, and finally top with remaining cheese and a final sprinkle of Italian seasoning.
Arrange ramekins on baking sheet and bake for 15 minutes or until heated through. If baking in a casserole dish instead of individual ramekins, bake for 20 to 25 minutes.
Turn on the oven broiler and broil for 2-3 minutes, watching carefully, until top is bubbly and cheese is browned in spots. Remove from oven and let cool for 5 minutes before serving.