1. Preheat oven to 350°F (175°C). Grease three 9-inch round pans with butter, line bottoms with parchment circles, grease parchment, and dust with flour.

2. In a large bowl, beat softened butter and granulated sugar on medium-high speed for 5 minutes until very light and fluffy.

3. Add eggs one at a time, beating well after each addition. Scrape bowl sides between additions.

4. With mixer on medium-low, slowly drizzle in vegetable oil over 1 minute until smooth and glossy.

5. In separate bowl, whisk together flour, baking powder, baking soda, and salt.

6. In measuring cup, whisk together sour cream, milk, vanilla extract, and butter extract.

7. Add dry ingredients to butter mixture in three additions, alternating with wet ingredients in two additions. Begin and end with dry ingredients. Mix on low just until combined.

8. Give batter final stir by hand with spatula, scraping bottom and sides.

9. Divide batter evenly among prepared pans (about 2⅓ cups per pan).

10. Bake 25-30 minutes until tops spring back when pressed and toothpick comes out clean.

11. Cool in pans 10 minutes, then invert onto wire racks. Peel off parchment and cool completely (2 hours).

12. For frosting: In heavy saucepan, combine brown sugar, butter, cream, and salt. Bring to boil over medium heat, stirring constantly.

13. Once boiling, stop stirring and boil exactly 3 minutes.

14. Remove from heat, stir in vanilla, and cool 10 minutes.

15. Beat in powdered sugar, 1 cup at a time, until spreadable consistency.

16. To assemble: Place one layer on serving plate. Spread with frosting while still slightly warm.

17. Repeat with second layer. Top with third layer.

18. Frost entire cake with remaining frosting, working quickly as it sets.

19. Let cake sit 30 minutes before slicing for frosting to set properly.