Preheat your oven to 325 degrees F. Trace the outline of 3 9-inch cake pans** on parchment paper. Cut out the circles and place in the bottom of each cake pan. See photos. With the paper in the bottom of the pan, use nonstick spray to grease each cake pan very well, including up the sides.***

In a large bowl or stand mixer, beat the butter until is is smooth. (You can actually start with cold butter if you have a stand mixer. Just beat a couple minutes, scraping sides, until it's smooth.)

Add 3 cups granulated sugar. Beat butter and sugar for 2 minutes, stopping once to scrape sides and bottom.

Add 1/2 cup light olive oil ("light" refers to the taste, not the calorie level. Sad, right? ;) Beat butter and sugar with the oil for 2 minutes, stopping to scrape once.

In a medium bowl (or in one of those giant 8 cup glass measuring cups, wish I had one), add 5 large eggs. Beat with a whisk until smooth. Add 1 cup buttermilk*, 1 tablespoon vanilla, and 1/2 cup full fat sour cream. Whisk it all together til smooth.

Place a fine mesh strainer over another medium bowl. Spoon and measure 3 and 1/4 cups all purpose flour into the strainer. Add 3/4 teaspoon salt and 1 tablespoon baking powder. Stir until it has all gone through the strainer and is sifted well.

Alternate adding the liquid and the flour mixture to the butter mixture, beating every time. I added half the liquid, stirred, half the flour, stirred, then repeated.

Mix ONLY until just combined. Scrape the bottom and sides to make sure it's all incorporated.

Divide the batter between the 3 prepared pans.

Bake the cakes at 325 for about 28-32 minutes.

Notes on baking: I like to bake my cakes one at a time because my oven is not exactly amazing. I've also done 2 cakes at a time though. I wouldn't do all 3 cakes at once, unless you have a pretty stellar oven that you trust.

However you choose to bake, make sure you rotate them 2/3 of the way through the bake time. This means turn the pan 180 degrees if there is one cake, or if there are two cakes, switch their places. The cake pans should NOT touch the edge of the oven.

Do NOT open the oven door at all, except for when you need to rotate the pans. Rotate the pans at about the 22 minute mark. If the whole top looks completely liquidy, do not rotate yet. You don't want to deflate your cake. Again, the total bake time for each cake is about 28-32 minutes.

Remove the cake/s from the oven. Let cool on a cooling rack for about 10-15 minutes. Use a knife to loosen the edge of the cake from the pan. Use your hand to invert the cake onto the cooling rack and continue cooling. At this point I often put them in the freezer for 20 minutes or so to speed up the cool time.

Make the frosting: Beat 2 cups butter until it is completely smooth.

Add powdered sugar one cup at a time. Add the cream in 1/4 cup increments in between cups of powdered sugar. Add 1 tablespoon vanilla and 1 teaspoon kosher salt. (less if you're using table salt) Beat until very fluffy, at least 2-3 minutes. Scrape the sides and bottom at least once or twice. 

Once all the cakes are completely cool, assemble your cake. Smear a bit of frosting on your cake stand so it doesn't go sliding off, then place your cake on the stand. Place several squares of parchment paper under the edge of your cake so that you don't get frosting all over your cake stand (see photos).

Add about 1 and 1/2 cups frosting (just eyeball it) to the top of the cake and spread evenly.

Add the next cake. Repeat.

Add the final cake. Add all the remaining frosting to the top of the cake. Spread it over the top of the cake, and then use an offset spatula to drag some of the frosting from the top over the edge of the cake. Keep moving the frosting all the way down. Continue this method until all sides and top are frosting.

If you want to make nice swirls like you see in the photos, use the back of a spoon.

Devour! Try not to eat it for breakfast like I did!