Preheat your oven to 375°F and grease your donut pan. I like to use shortening or butter to grease my pan.
In the bowl of a stand mixer fitted with a paddle attachment (or a regular mixing bowl - this recipe can be made either way!) mix the cake flour, salt, baking powder, and lemon zest together.
In a separate bowl, combine the whole milk, sugar, lemon juice, egg, vanilla extract, and melted butter. Whisk until smooth.
With the stand mixer on low, slowly pour the wet ingredient mixture into the dry ingredient mixture. Mix until just combined.
Transfer the donut batter into a piping bag and pipe each section of the donut pan 2/3-3/4 the way full.
Place in the oven and bake at 375°F for 15-20 minutes, or until an inserted toothpick comes out clean. While your donuts are baking, let's make the raspberry glaze!