- Preheat oven to 350 degrees.
- In a small saucepan, warm buttermilk over low heat until bubbles form around edges of the pan then pour over polenta or cornmeal in a small bowl. Let stand for one hour to soften.
- In stand mixer using paddle attachment, cream together butter and sugar. Add eggs, lemon zest, and vanilla and beat until blended.
- Place flour, baking powder, baking soda, and salt in a separate bowl, and whisk to combine.
- Add dry ingredients to butter mixture alternating with buttermilk mixture, and beginning with dry. Mix until combined. Add batter to prepared pan, and smooth cake surface.
- Place pan in water bath and bake until a toothpick inserted into center of cake comes out clean.
- Let cake cool in the pan for 10 minutes. While cake is still warm, drizzle with lemon caramel sauce.
Lemon Caramel Sauce
- Pour sugar into center of a deep saucepan, and add water.
- Bring to a full boil a over high heat, and cook without stirring until sugar is amber-colored caramel, about 10 to 15 minutes. Swirl mixture occasionally to even out color.
- Carefully add lemon juice and vanilla and wait for caramel to bubble and subside. Finish with butter.