Preheat your oven to 350°F (175°C) and prepare two 6 or 7-inch cake pans by greasing them with butter and flour. Line with parchment paper.

In a small bowl, combine milk with apple cider vinegar or lemon juice and let it sit for 5 minutes.

Place ground pistachios and sugar into a food processor and pulse until finely ground.

In a medium bowl, whisk together flour, baking powder, salt, and ground pistachio mixture until well combined.

In a separate large bowl, whisk together the buttermilk substitute, olive oil, and both vanilla and almond extracts.

Gently fold the dry ingredients into the wet ingredients using a spatula until just combined.

Evenly divide the batter between the prepared cake pans and smooth the tops. Bake for 25-30 minutes until a toothpick comes out clean.

Once baked, cool the cakes in the pans for 10 minutes before transferring to a wire rack to cool completely.

In a bowl, beat room temperature butter and blackberry preserves until smooth. Gradually mix in powdered sugar, vanilla, salt, and thyme.

Level the tops of cooled cake layers. Stack with frosting and preserves between layers, frost the sides and top, and garnish.