Preheat the oven to 375 degrees F (190 degrees C). Line 2 muffin tins with cupcake liners.

Toast sesame seeds in a dry frying pan over medium heat, stirring and tossing constantly, until fragrant, about 2 minutes. Omit this step if the seeds are already toasted.

Beat butter and sugar in a large bowl using an electric mixer until creamy. Add toasted seeds, eggs, sesame paste, and vanilla extract. Beat until combined. Gradually beat in flour, baking powder, and salt. Add milk and beat for a few more minutes until combined.

Fill cupcake liners with the batter.

Bake in the preheated oven until a toothpick inserted into a cupcake comes out clean, 16 to 18 minutes.