Preheat your oven to 350°F (177°C). Prepare three 8-inch round cake pans by lining with parchment paper and lightly greasing them.

In a mixing bowl, combine sour cream, eggs, honey, canola oil, and vanilla extract, stirring until smooth. In another bowl, sift together flour, baking soda, baking powder, and salt. Gradually mix dry ingredients into wet mixture until just combined.

Divide the cake batter among prepared pans. Bake for 24-26 minutes or until a toothpick inserted comes out clean. Cool in pans for 5-8 minutes, then transfer to a wire rack and refrigerate for 30 minutes.

In a food processor, blend shelled salted pistachios with heavy cream until a smooth paste forms. Beat softened unsalted butter until fluffy, then mix in the pistachio paste and confectioner’s sugar until light and airy.

Level domed tops of cake layers if necessary. Split each layer in half horizontally, drizzle honey on cut sides, spread buttercream and sprinkle finely diced pistachios. Repeat with remaining layers, finishing with a final layer of buttercream on top.

Apply a thin layer of buttercream around the entire cake for a crumb coat. Chill in the refrigerator for 30 minutes to set.

Apply a final layer of pistachio buttercream over the entire cake, smoothing with a spatula. Garnish with extra pistachios and drizzle honey on top.

Refrigerate the cake for 1-2 hours before serving for flavors to meld. Allow to soften at room temperature before serving.