Preheat oven to 350°F (180°C). Butter a 9-inch round cake pan. Line bottom of pan with parchment paper. Lightly dust sides of pan with cocoa; tap out excess.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
In a medium bowl, whisk together cocoa and ½ cup (120 grams) boiling water until smooth. Whisk in milk. Add avocado oil, eggs, and vanilla, and whisk until combined. Add cocoa mixture to flour mixture, whisking just until combined. (Batter will be thin.) Pour batter into prepared pan.
Bake until a wooden pick inserted in center comes out clean, 35 to 45 minutes. Let cool in pan for 10 minutes. Run an offset spatula around edges of pan. Remove from pan, and let cool completely on a wire rack. Spread Chocolate Frosting on top of cooled cake.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/chocolate-avocado-oil-cake-chocolate-frosting/