In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs, one at a time, beating well after each addition. Beat in vanilla.
In a medium bowl, whisk together flour, ancho chile pepper, baking soda, and salt. With mixer on low speed, gradually add flour mixture to butter mixture alternately with milk, beginning and ending with flour mixture, beating just until combined after each addition. Transfer half of batter to a medium bowl; stir in dark cocoa until smooth. Stir cocoa into remaining batter until smooth.
Spray a 10-cup Bundt pan with baking spray with flour. Using 2 (¼-cup) spring-loaded scoops, alternately scoop batters into prepared pan. Tap pan on a kitchen towel-lined counter a few times to settle batter and release any air bubbles.
Bake until a wooden pick inserted near center comes out with a few moist crumbs, 45 to 50 minutes. Let cool in pan for 10 minutes. Remove from pan, and let cool completely on a wire rack. Spoon Chocolate Glaze over cooled cake.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/mexican-hot-chocolate-bundt-cake/