Preheat oven to 375°F. Oil a 10x2-inch round baking dish with 1 tablespoon of olive oil.
In a large bowl, sift together flour, baking powder, and salt. Make a well in the center and add water, olive oil, mint, onions, and olives. Stir with a wooden spoon until the dough comes together. Turn out onto a lightly floured surface and knead until the dough is smooth, about 10 minutes. (The dough will be moist because of the olives.) Cover and let rest for 10 minutes.
Shape dough into a ball and then pat down gently with the palms of your hands to fit into the baking pan. Bake at 375°F for 50 minutes to 1 hour, until the surface is golden brown. Remove from oven and immediately remove from pan. Cool on a rack before serving.