• Preheat your oven to 160 C/ 325 F. Butter a 6 inch round pan and dust with flour well.
• Whisk together the flour, baking powder and salt. Keep aside.
• Beat the butter and sugar together until light and fluffy.
• Add the eggs , and then the yolks and the vanilla one by one , beating well after each addition .
• Now, alternately add the flour mixture and milk mixture beating after each addition. So add 1/3rd of the flour -1/2 of the milk - 1/3rd of the flour- 1/2 of the milk- 1/3rd of the flour. Scrape the bottom and sides of the bowl as necessary.
• Pour batter into pan and bake at 160 C/ 325 F for 38-45 minutes until a toothpick inserted comes out dry and the top springs back on touching.
• Cool in pan for 5 minutes and completely on wire rack.

For the buttercream

• Whisk the egg whites and sugar in a metal bowl for a minute .
• Place bowl over a saucepan with an inch of water (double boiler method) and bring the water to a simmer while whisking constantly.
• Whisk and heat until all the sugar has dissolved , or a thermometer shows 160 F / 70 C.
• Take off heat (and the saucepan) and start beating at medium high speed until stiff peaks are formed and the outside of the bowl is cool.
• Add butter , one cube (tablespoon) at a time while whipping. Repeat with all the butter.
• Beat at high until desired consistency is achieved.
• Add the jam and beat for 3-5 minutes more to remove any air bubbles.

To assemble

• Using a serrated knife , cut off the top crust / dome of the cooled cake.
• Slice the cake into three equal layers.
• Spread about 1/4 cup buttercream on one of the layers.
• Place another layer on top, press down gently and spread about 1/4 cup buttercream.
• Place the third layer on top, press down gently . Spread buttercream on top and sides.
• Chill for 20 minutes and then using a spatula, smooth the buttercream on top and sides.