Whisk egg whites and salt in a large bowl until foamy. (You can use a hand mixer or a food processor. The foam doesn't have to be super-stiff.)
Combine gluten-free flour with egg whites. Add baking powder. Don't worry about the lumps, they will disappear later.
Combine egg yolks with oil and pour over the foamy egg whites. Mix slowly using a spatula.
Add olives. Mix slowly until well blended together.
Grease a 30x10cm pan with some oil and powder it with flour.
Add 1/2 of the batter and spread evenly. Spread the red pesto on top and cover with the other half of the batter. Alternatively, you can add all the batter and pour the pesto on top.
Bake in the preheated oven at 180C for 25min. Check with a toothpick if ready.