Preheat an oven to 350 F.
Prep the bundt pan. Grease your bundt pan really well and dust it with cocoa powder, shaking off any excess. Place the bundt pan on a rimmed baking sheet and set it aside.
Mix the dry ingredients. In a mixing bowl, whisk together the sugar, flour, cocoa powder, baking soda, baking powder, and salt until everything is evenly mixed.
Mix the wet ingredients. In a large measuring cup, whisk together the eggs, sour cream, oil, vanilla, and guinness until very smooth.
Mix the wet ingredients into the dry. Whisk the wet ingredients into the dry until everything is almost mixed. Switch to a rubber spatula, pour the hot coffee over the top, and fold the batter until no streaks of flour remain.
Bake. Pour the batter into the prepared bundt pan and transfer to the oven. Bake for 45-55 minutes, until the cake is puffed but soft and a cake tester comes out clean. Cool the cake for 20 minutes in the pan, then invert onto a plate or cooling rack to finish cooling to room temperature.
Make the frosting. Add the softened cream cheese and butter to a mixing bowl. Use a hand mixer to beat the two together until smooth. Add the vanilla and powdered sugar and beat on low until smooth. Finally beat in the bailey's until smooth.
Frost the cake. Spread the frosting all over the cooled bundt cake in an even layer. Drizzle the salted caramel all over the top and sprinkle with flaky sea salt, if desired.