as a bakery lover, Seongsu is one of the place that I frenquently visit! 

Bakery Onion is a famous one, nobody would have missed their signature Pandoro :) 

another two bakeries are close to Ttukseom station, one is called 'Meal-do'(밀도), they make amazing toast, one of their signature toast is a cat-face shaped toast. Lemon scone and cream cheese bread also taste very good.

Last but not least, Seongsu Baking Studio. this bakery is famous in the neighborhood, you might miss it if you're not familiar with this area. They serve best salt bread and baguette here, jambon beurre is also yummy!

If you enjoy bakeries like me, these 3 spots are worth a try!^^