Preheat the oven to 350°F. Grease two 8-inch round cake pans and line the bottoms with parchment paper, then stir the almond milk and lemon juice together and set aside.
In a food processor, pulse the pistachios with 1/4 cup of the sugar until finely ground, stopping before it turns into a paste. Transfer to a bowl and whisk in the flour, baking powder, baking soda, and salt.
In a large bowl, beat the butter and remaining 1 1/4 cups sugar on medium-high speed for 3 minutes until fluffy, then beat in the oil. Add the eggs one at a time, then beat in the vanilla and almond extract.
With the mixer on low, add the pistachio flour mixture in three additions, alternating with the almond milk mixture, beginning and ending with the dry ingredients. Mix just until combined.
Divide the batter between the pans and bake for 28 to 33 minutes, until a toothpick comes out clean. Cool in the pans for 10 minutes, then turn out onto a wire rack to cool completely.
For the frosting, beat the butter and pistachio butter until smooth. Gradually add the powdered sugar, then add the almond milk, vanilla, and salt and beat on medium-high for 3 minutes until fluffy.
Place one cake layer on a serving plate, spread with frosting, and top with the second layer. Frost the top and sides, sprinkle the chopped pistachios over the top and around the base, and chill for 20 minutes before slicing.