Preheat oven to 375°F. Line 30 cupcake pan cups with paper liners.
Sift the self-rising flour and salt together in a bowl. In another bowl, beat the unsalted butter and sugar with an electric mixer until light and fluffy, about 2 minutes.
Mix in the eggs one at a time, beating each egg until incorporated before adding the next. Mix in the vanilla extract and lemon zest.
Gently combine the flour mixture into the butter mixture, one third at a time, alternating with half the milk and half the lemon juice after each of the first 2 additions of flour. Beat until just combined; do not over mix.
Fill the prepared cupcake liners with batter 3/4 full, and bake in the preheated oven until a toothpick inserted in the center comes out mostly clean, about 15 minutes. Let the cupcakes cool in the pans for about 10 minutes before removing them to finish cooling on a rack.
