Preheat oven to 350°F (175°C). Grease and flour a bundt pan, making sure all corners are well coated.
Pour melted butter into the pan, sprinkle brown sugar over it, then arrange pineapple chunks on top.
In a large bowl, beat softened butter and granulated sugar for 3–4 minutes until light and fluffy.
Mix in eggs one at a time, beating well after each. Scrape down the bowl as needed.
In a separate bowl, sift together flour and baking powder.
Add flour mixture in three parts, alternating with sour cream. Start and end with flour. Mix until just combined.
Fold in crushed pineapple, vanilla, and optional pineapple extract. Mix gently until evenly blended.
Pour batter over pineapple topping in the pan. Smooth the top and bake for 50–60 minutes until a toothpick comes out clean.
Let cake cool in the pan for 10 minutes. Invert onto a serving plate and let it cool completely.
In a saucepan, combine brown sugar, heavy cream, and butter. Stir over medium heat for 3 minutes until smooth and slightly thick. Remove from heat and stir in vanilla.
Drizzle warm caramel over cooled cake. Let it soak in, slice, and serve.