Preheat oven to 350 degrees. Prepare 2- 8 inch pans by lining the bottom of each with a round of parchment paper. No need to grease the sides.
In a small bowl, mix together flour, baking powder, and salt.
In a large bowl with an electric mixer, beat butter and sugar for a few minutes--until mixture is light and fluffy. Add eggs and beat a few minutes more. The mixture will look almost white. Beat in vanilla.
Add flour mixture and beat until just combined. Scrape into prepared pans. Thump each pan on counter to release any trapped air bubbles.
Bake at 350 for about 20 minutes or until tester comes out clean. Remove from oven. Cool cakes in pans for 5 minutes before turning out onto wire rack to cool completely.
Once cakes are cool, spread jam onto the top of one of the cakes. Place the other cake on top of the first cake. You may now dust top of cake with sifted confectioner's sugar (if using).