Preheat oven to 350°F. Line an 8x8-inch baking dish with parchment paper or spray with nonstick cooking spray.
In a large bowl, combine flour, sugar, cocoa powder, salt, and baking soda. Whisk to combine.
Add vanilla, vinegar, oil, and water to the dry ingredients and stir using a spatula or whisk until ingredients are fully combined.
Pour batter into the prepared pan and bake for 30-35 minutes. When an inserted toothpick is removed with a few crumbs (not clean!) the cake is done. Let it cool while you prepare the frosting.
With a hand-held mixer, combine room temperature butter, cocoa, honey, vanilla, and confectioners sugar.
Turn mixer on low and let it combine ingredients for about 30 seconds.
Slowly add milk, one tablespoon at a time, until you reach desired consistency. You may not need all 3 tablespoons, you may need 1 more, it can vary from season to season and kitchen to kitchen.