Preheat oven to 350℉. Grease the two cake pans, dust pans with flour and tap out any excess

In a large bowl,whisk together flour,baking powder,baking soda,salt and 11/2 cups sugar, in another bowl, whisk together the melted butter, butter milk, oil,vanilla, lemon zest,rosemary and egg yolks

For the meringue, in a bowl beat egg whites at a medium speed until foamy. With machine running,stream in the remaining 1/4 cup sugar, beat at high speed just until stiff peaks form. Gently transfer to a bowl and set aside

Add flour mixture to the empty stand mixer bowl fitted with whisk attachment.with mixer running at a low speed, gradually pour in butter mixture and mix for about 10sec.mix until combined

Gently fold in 1/2 of the meringue just until incorporated. Then fold in the rest of the meringue. Be very gentle to not deflate the air in the meringue. You will have few white streaks in the butter. Divide butter evenly between your prepared cake pans

Place pans on a half sheet pan and bake on the center rack in the oven for 20-25min. Bake until the cake layers begin to pull away from sides of pan

When it's ready cool cakes in pans on wire rack for20 min. Run a thin bladed knife around the sides of the pans to loosen cakes then invert on a greased wire rack, allow to cool completely before frosting

For the frosting. Combine all the ingredients in the bowl. Mix on medium speed until combined and creamy

Enjoy your fluffy lemon cake with some cool drink