Preheat your oven to 350°F (177°C) and prepare three 8-inch round cake pans.

Combine the sour cream, eggs, honey, cooking oil, and vanilla extract in a large mixing bowl.

In a separate bowl, whisk together the flour, baking soda, baking powder, and salt.

Gradually add the dry mixture to the wet ingredients, stirring gently to combine.

Divide the batter evenly among the prepared cake pans and bake for 24-26 minutes.

Allow the cake layers to cool in their pans for about 5-8 minutes, then turn them out onto a wire rack.

Blend pistachios with heavy cream in a food processor to form a smooth paste.

Beat the softened butter until fluffy, then mix in the pistachio paste and confectioner's sugar.

Level the cooled cake layers in half horizontally for thinner layers.

Assemble by spreading buttercream and honey between layers, stacking them.

Refrigerate the assembled cake for about 30 minutes to set the crumb coat.

Apply a final layer of buttercream and garnish with diced pistachios and a drizzle of honey.

Chill the decorated cake in the refrigerator for 1-2 hours before serving.