Heat oven to 350 deg.
Heat brown sugar and pineapple juice in 8“ square baking pan (alternative: 9” round). Cook until mixture is bubbly and starts to thicken. Remove from heat and whisk in butter and vanilla. When mixture has slightly cooled press in the pineapple chunks and set aside. Allow to harden prior to cake addition.
In medium dry bowl whisk FLOUR, CORNMEAL, BAKING POWDER, and SALT; set aside.
In larger wet bowl whisk GRANULATED SUGAR, BROWN SUGAR, EGGS together until thick and homogeneous, about 45 sec. Slowly whisk in BUTTER until combined. Add SOUR CREAM and VANILLA, whisk until combined.
Add dry flour mixture to wet mixture and mix until just combined.
Pour batter into pan and spread evenly over fruit. Cover pan tightly with cover or aluminum foil. Bake until golden, center of cake has solidified and toothpick inserted into center comes out clean, 60-70 min.
Cool pan on wire rack 35 min. Run knife around sides of pan to loosen. Place plate over cake pan and invert. If fruit sticks to bottom, remove it and stick on top of cake.