Preheat the oven to 350°F (175°C).

Grease two 6” or 7” cake pans with butter, then dust with flour. Line the bottoms with parchment paper rounds.

In a medium measuring cup, whisk together milk and apple cider vinegar; let it rest for 5 minutes to create homemade buttermilk.

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

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

In a large bowl, whisk together the buttermilk mixture, olive oil, and both extracts until smooth. Optionally, add food dye for color.

Fold the dry ingredient mixture gently into the wet ingredients using a spatula.

Divide the batter evenly between the two prepared pans (around 425g of batter each).

Bake for 25-30 minutes, or until a toothpick inserted comes out clean.

Cool the cakes completely in the pans on a wire rack. For best results, wrap and chill the layers in the fridge overnight before assembling.

Beat butter with blackberry preserves until smooth.

Gradually mix in powdered sugar, then add vanilla, salt, and thyme.

Cream until fluffy (about 4-5 minutes). Level the cakes if needed.

Place the leveled cake layer cut side up on a cake stand. Spread some buttercream in the middle, followed by a spoonful of blackberry preserves.

Add the second layer on top. Decorate with remaining buttercream, more blackberry preserves, fresh blackberries, and chopped pistachios.

Slice, serve, and enjoy every bite!