A one-bowl almond cake covered in Swiss meringue buttercream and edible flowers.
Preheat over to 350º F.
Add the sugar, flour, baking powder and salt to the bowl of a stand mixer and whisk together. Beat in the butter and oil with the paddle attachment until the mixture looks like wet sand.
Mix the milk, vanilla and almond extract in on medium low speed. Add the eggs one at a time, mixing after each one until incorporated.
Divide between three 6" cake pans greased and lined with parchment. Bake until a toothpick comes out clean. Start checking for doneness around 30 minutes. Let cool in the pans for five minutes then turn onto a rack to cool completely before frosting.
Add the egg whites and sugar to the bowl of a stand mixer, making sure the bowl is very clean first. Place over a pot of simmering water (but don't let the bottom of the bowl touch the water). Whisk constantly until the sugar is dissolved and the mixture is very hot. If you used regular egg whites, use a thermometer to make sure the mixture reaches 160º. For pasteurized egg whites, you don't need a thermometer.
Place the bowl back on the stand mixer fitted with the whisk attachment. Whisk on medium high speed until the mixture turns into voluminous, glossy meringue and the bottom of the bowl has cooled to room temperature. The meringue should be stiff enough that it won't slide out of the bowl if you turn it upside down.
Switch to the paddle attachment and begin incorporating the butter, one tablespoon at a time, on medium low speed. Wait until each tablespoon is mixed in before adding another. Don't worry if it looks curdled or separated.
Once all the butter is added, scrape down the sides of the bowl and mix on medium high speed until the buttercream is smooth and fluffy. If it hasn't come together after 5 minutes, it may be too warm. Refrigerate for 5 minutes then try mixing again. Mix in the vanilla and salt.
Frost and decorate the cake as desired. Serve at room temperature.
You can bake the cake layers and make the buttercream in advance. Wrap the cooled cake layers in plastic and freeze to keep them fresh (this can make frosting easier too). Let refrigerated buttercream come to room temperature (it can take a few hours) and remix until it's fluffy before using.