Preheat the oven to 375°F. Spray the regular sized donut pan with non-stick baking spray with flour.

Beat the butter and sugars until creamy. Add the egg, vanilla, and yogurt and beat again.

Stir together the baking powder, baking soda, and flour. Alternately add the flour mixture and Key lime juice to the butter mixture until mixed together. Do not over mix the batter.

Gently stir in the blueberries. Spoon half the batter into the prepared donut pan cavities. Do not fill each one more than 3/4 full. Bake for 12 minutes.

Let the donuts cool in the pan for 3-4 minutes, and then gently remove by loosening all around the edges with a knife. Remove and place on a cooling rack until completely cool. Repeat with the remaining batter.

Whisk together the powdered sugar and Key lime juice. Use a knife to spread the glaze on top of the cooled donuts.

Add a little bit of green gel food coloring to the remaining glaze. Spoon into a plastic baggie and cut on tip off. Drizzle over the glazed donuts. Let the glaze set. Store in a loosely sealed container.