Make the crust if not already made (see recipe notes, or Gluten-Free Whole Grain Pie Crust)
Pre-heat your oven to 400 degrees F or 200 degrees Celsius
Chop your green onions, slice your tomatoes, grate your cheese, and finely chop the spinach, preferably in a food processor
Whip 6 eggs well then beat in the tapioca flour and baking powder
Layer the green onions in the bottom of the crust
Sprinkle 1/3 of the cheese mixture on top of the onions
Combine the spinach with the egg mixture
Pour the egg-spinach mixture on top of your green onions. Smooth evenly in the crust with a wooden spatula or spoon
Sprinkle another 1/3 of the cheese
Whip 5 more eggs up plain and pour as the next layer
Cover the top with the basil leaves
Layer the thick slices of tomato on top of the basil
Sprinkle the rest of the cheese on top
Push the tomatoes down into the egg so they are well nestled in the quiche
Bake for 20 minutes, then turn your temperature down to 350 degrees F, or 180 degrees Celsius for the remaining time, until the quiche rises above the top of the pan, the crust pulls away from the side, and a knife inserted in the middle comes out without any runny egg, or about 15-25 more minutes, depending on your oven.