Cream the butter and lemon sugar on medium-high for 3 minutes until pale and fluffy.

Add the eggs one at a time, beating after each. Mix in the vanilla and lemon juice.

Toss the blueberries with 1 tablespoon of the flour and set aside.

Whisk the remaining flour with the baking powder, baking soda, and salt.

Add the dry mixture and buttermilk alternately, beginning and ending with dry, in five additions. Mix on low just until combined.

Fold in the floured blueberries by hand.

Grease a 7-inch bundt pan thoroughly, including the flutes. Fill no more than two-thirds full.

Air fry at 310°F for 30–35 minutes, tenting with foil after 20 minutes if browning quickly. The center should reach 200–205°F.

Cool in the pan 10 minutes, then invert onto a rack and cool completely, about 45 minutes.

For the frosting, beat the cream cheese and butter smooth. Add the powdered sugar, lemon juice, and salt; beat 2 minutes until fluffy.

Pipe thick ribbons from the outer edge toward the center hole. Refrigerate until serving.