Preheat the oven to 350°F (177°C). Grease a10–12 cup bundt pan generously with butter, then dust with cocoa powder and tap out the excess.
In a medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.
1¾ cups (247g) all-purpose flour, ¾ cup unsweetened cocoa powder, 1½ teaspoons baking soda, 1 teaspoon baking powder
In a separate large bowl, whisk the oil, sugar, eggs, milk, and vanilla until smooth. Add the dry ingredients to the wet ingredients and whisk until just combined. Slowly pour in the hot water and whisk until the batter looks smooth and thin. Fold in the chopped pecans.
½ teaspoon salt, ¾ cup vegetable oil, 1¾ cups (350g) granulated sugar, 2 large eggs, 1 cup whole milk, 1 teaspoon pure vanilla extract, 1 cup hot water, 1 cup chopped pecans
Pour the batter into the prepared pan. Bake for 45–55 minutes, or until a toothpick inserted into the center comes out mostly clean.
Cool the cake in the pan for 15 minutes, then invert onto a wire rack and allow it to cool completely before decorating.
To make the frosting, in a medium mixing bowl, beat the softened butter until smooth and creamy. Add the powdered sugar gradually until completely combined. Add the caramel sauce and vanilla. Beat until the frosting becomes fluffy, thick, and smooth. If you prefer a firmer texture for piping, add a bit more powdered sugar. Transfer the buttercream to a piping bag fitted with a large round tip.
1 cup salted butter, 3 cups powdered sugar, ½ cup caramel sauce, 1 teaspoon pure vanilla extract
To assemble, using a piping bag with a small round tip, pipe thick ribbons of caramel buttercream over the cooled bundt cake in a back-and-forth motion. Warm the caramel and chocolate sauces just until pourable. Drizzle the caramel sauce over the buttercream, followed by the chocolate sauce, letting both drip naturally down the cake. Sprinkle chopped pecans generously over the top. Add an extra drizzle of caramel right before serving if you want a glossy finish.
chocolate sauce, 1 cup chopped pecans, caramel sauce