Preheat oven to 350 degrees Fahrenheit. Grease 2 mini bundt pans (4 molds in each pan). Juice and zest the lemon and set aside 2 ½ teaspoons lemon juice and 1 tablespoon lemon zest.
In a large bowl, whisk together the egg yolks, sugar, the remaining lemon juice and zest, honey, applesauce, and avocado oil.
Using a stand or handheld mixer, beat the egg whites with a sprinkle of sugar. Keep beating until it start to peak, about 5 minutes.
Sift in the flour and salt to the lemon mixture and fold to combine. Fold in the egg whites. When everything is incorporated, sift in the baking powder and soda. Mix until just combined.
Pour the batter in the prepared pans about halfway full. Bake for 15 minutes.
For the icing, whisk together powdered sugar and the reserved lemon juice and zest in a small bowl.
Transfer the cakes to a cooling rack. Once they have cooled, glaze with the icing.