Preheat your oven to 350°F (177°C). Grease two 8-inch round cake pans and line the bottoms with parchment paper. In a bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed until light and fluffy, about 4 minutes. Drizzle in the honey and beat until combined. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Add the dry ingredients to the wet mixture in three additions, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix on low speed just until combined after each addition.
Divide the batter evenly between the two prepared pans and smooth the tops. Bake for 28 to 32 minutes until the cakes are golden and a toothpick inserted in the center comes out clean. Let them cool in the pans for 10 minutes, then turn out onto wire racks to cool completely.
Make the buttercream by beating the softened butter with an electric mixer on medium-high speed until pale and creamy, about 3 minutes. Add the powdered sugar one cup at a time, beating on low speed after each addition. Mix in the honey, heavy cream, vanilla extract, and flaky sea salt. Beat on medium-high for 2 minutes until light and fluffy.
Place the first cake layer on a serving plate. Spread a thick layer of buttercream on top. Set the second layer on top and frost the top and sides with the remaining buttercream, creating rustic swoops with a spatula.
Drizzle honey over the top of the cake and finish with a generous pinch of flaky sea salt. Slice and serve at room temperature.