Preheat the oven to 350F. Grease two 6” or 7” cake pans with butter, then dust with flour. Line the bottoms with parchment paper rounds. Set aside.

In a medium measuring cup or bowl, whisk together the milk and apple cider vinegar; allow to rest for 5 minutes.

Add the pistachios and sugar to a food processor or blender, and blend until finely ground.

In a medium bowl, whisk together the pistachio/sugar mixture, flour, baking powder, and salt. Set aside.

In a separate large bowl, whisk together the milk/apple cider vinegar mixture, olive oil, and both extracts until well combined.

Add the dry ingredient mixture to the wet, and use a spatula or wooden spoon to gently fold until just combined.

Divide the cake batter evenly among the two prepared cake pans (about 425g of batter should be in each).

Bake at 350F for 25-30 minutes, or until a toothpick inserted into the middle comes out clean.

Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan. It is recommended to wrap and chill the layers in the fridge overnight before assembling.

Prepare the buttercream. In a mixing bowl, beat the butter with the blackberry preserves until smooth.

While mixing on low, add spoonfuls of the powdered sugar until fully combined. Then, beat in the vanilla, salt, and thyme.

Increase the speed to medium, and beat for 4-5 minutes, until very light and fluffy.

If needed, slice the top of one cake layer off to even. Leave the other one with the domed top.

Place the evened cake layer cut side up on a cake stand or platter. Spread or pipe some of the buttercream in the middle, then pipe or spread some around the edges to create a border. Add a large spoonful of blackberry preserves to the middle.

Add the second cake layer on top, and pipe or spread the remaining buttercream on top. Add another large spoonful of blackberry preserves into the middle, then garnish with fresh blackberries and chopped pistachios, if desired.

Slice and serve.