Pre-heat the oven to 375 degrees. Lightly mist a 12 count standard-sized muffin tin with cooking spray and set aside.
Place the strawberries, rhubarb, lemon juice and powdered sugar in a bowl and stir to combine. Set aside.
In a large mixing bowl, add the egg, applesauce, sugar, and vanilla and stir together until well combined. Add the melted butter and stir until well combined.
In a separate mixing bowl, add the flour, baking soda, baking powder, and salt and stir until combined. Add the dry ingredients to the wet ingredients and stir together until combined into a batter. Add the strawberry rhubarb mixture from step two and stir to combine.
Spoon the batter evenly amongst the wells in the prepared muffin tin. Bake for 18-20 minutes.