Step 1In a large, heavy-bottom saucepan, combine the beer and sugar. Bring the mixture to a boil over high heat while whisking. Continue to boil the mixture until it is reduced to 3/4 cup plus 3 tablespoons (7.5 ounces), about 15 minutes. Immediately remove from heat and place in a bowl or measuring cup to cool to room temperature. The mixture will thicken as it cools. This makes more syrup than is required for the rest of the recipe; the rest of the syrup will keep, covered and refrigerated, up to 2 weeks.
Step 1Heat the oven to 350 degrees. In a large bowl, sift together the flour, baking powder and salt.
Step 2In the bowl of a stand mixer, or in a large bowl using a hand mixer, beat the butter until soft, about 2 minutes. With the mixer running, slowly add the sugar and continue to mix until the mixture is light and fluffy, 2 additional minutes. Add the eggs, one at a time, until fully incorporated.
Step 3In a large measuring cup or medium bowl, combine the milk, Tecate and vanilla. The milk will start to curdle -- this is normal (the milk fats are reacting to the acidity of the beer). Set aside.
Step 4With the mixer running, add 1/3 of the dry ingredients to the butter mixture. Scrape the bowl and add 1/2 of the combined liquids. Add half the remaining dry ingredients, then the remaining liquid. Add the remaining dry ingredients and continue to mix until everything is fully incorporated.
Step 5Add 5 tablespoons of the Tecate syrup to the batter, stirring to combine. Pour the batter into a greased and floured 10-cup bundt pan, filling the pan about 3/4 full.
Step 6Bake the cake until a toothpick inserted comes out clean, about 50 minutes, rotating halfway for even baking. Invert the cake onto a cooling rack to cool.
Step 7While the cake is still warm, drizzle the remaining 6 tablespoons Tecate syrup over it, letting the syrup absorb into the cake. Continue to cool the cake until cool to the touch, then frost if desired.
Step 1In the bowl of a stand mixer, or in a large bowl, cream the butter. With the mixer running, slowly add the powdered sugar until fully incorporated. Blend in the Tecate syrup, then add milk to thin to desired consistency. This makes 3 to 4 cups frosting.