Melt the butter in a medium saucepan over medium heat, swirling occasionally. When the butter just reaches boiling temperature remove it from heat, stir in the tea and steep for an hour or more. Strain the tea, forcing the excess butter out of the tea leaves with the back of a spoon. Cool the butter to room temperature before using.
Preheat oven to 350 degrees. Prep 3 x 6 inch cake pans by buttering them, lining the bottoms with rounds of parchment paper, then dusting them with flour and tapping out the excess.
Beat the butter and sugar until pale and fluffy, then add the egg whites gradually, beating to combine, about 2 minutes.
Sift the flour, baking powder, salt and ground vanilla beans together in a bowl and set aside. Mix the buttermilk and vanilla extract (if using) together and set aside.
Add the dry ingredients in 3 additions, alternating with the buttermilk mixture, mixing just until combined or finishing by hand.
Distribute the batter evenly into the prepared pan and smooth with a spatula or the back of a spoon. Gently tap the pans on the counter a couple of times to release any air bubbles trapped in the thick batter. Bake for 20 minutes, then rotate the pans in the oven and bake for an additional 5-10 minutes, checking every 3 minutes for doneness. A toothpick inserted into the center of the cake should come out clean and the top should spring back to the touch. Place on cooling racks until the pans are cool enough to handle, then run a knife around the edges of the cake to loosen it and turn it out onto the cooling racks to come to room temperature.Assembly// Level the cakes if desired. Place the first layer face up on a cake board or serving plate and smooth a generous layer of buttercream on top. Distribute about ¼ c raspberries on top of the buttercream and place the second layer on top. Repeat, and place the last layer face down (so the smooth side is up) and press to secure. Place the cake in the fridge for a few minutes to firm up the buttercream and make icing the cake easier. Roughly ice the top and outsides of the cake and drizzle ganache around the edges of the cake. Decorate with flowers or as desired. Serve at room temperature. May be refrigerated for up to 3 days.
Recipe by oh honey bakes at https://ohhoneybakes.com/jasmine-butter-cake-raspberry-buttercream/