Preheat oven to 300 degrees F (150 degrees C). Line 2 baking sheets with parchment paper.

Beat egg whites in a glass, metal, or ceramic bowl until stiff peaks form. Gradually add sugar, 1 teaspoon at a time, while continuing to beat at high speed. Combine ground almonds and cinnamon in a bowl and fold into the egg white mixture with a spatula. Add more ground almonds if mixture is too runny.

Use 2 teaspoons to place little mounds of almond mixture 2 inches apart onto the prepared baking sheets.

Bake in the preheated oven until lightly browned and baked through, 15 to 20 minutes. Carefully remove from baking sheets and cool on wire racks.