To bake the cake:

1. Oven and pan prep: Preheat oven to 350°F. Grease a 9”x 5” loaf pan with nonstick cooking spray. 
2. Combine the dry ingredients: In a medium mixing bowl, whisk together the gluten-free flour, corn starch, salt, and baking soda.
3. Cream butter, sugar, and eggs**: In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar on medium-high speed until light and fluffy. Beat in the eggs one at a time on medium-low speed, mixing each in until incorporated, and scraping down the bowl and beater as needed. Once all of the eggs have been added, add the vanilla extract, increase speed to medium, and beat just until fully and evenly combined.***
4. Alternate adding the liquid and dry ingredients: With the mixer on low speed, carefully add about ⅓ of the flour mixture, followed by half of the sour cream, mixing each in until partially incorporated before moving on to the next addition. Continue in this way, adding another ⅓ of the flour mixture, the remaining sour cream, and finally the remaining flour mixture. Keep beating at low speed just until all ingredients are evenly incorporated; the batter should be thick and smooth.
5. Bake: Transfer the batter to the prepared loaf pan, using a spatula to spread it evenly into the pan and smooth out the top surface. Bake in the preheated oven for 70-75 minutes, or until a toothpick inserted into the center of the loaf comes out clean. 
6. Cool: Cool bread in pan over a wire rack for about 30 minutes, and then transfer the loaf directly to the rack to finish cooling.

Grilling and Serving: 

1. Grill: Heat grill at medium-low heat. Cut loaf into 1” thick slices and brush each side with melted butter. Sprinkle pineapple slices with raw or demerara sugar. Grill cake for 1-2 minutes per side, and pineapple slices for 2-3 minutes per side, uncovered. Serve warm, with whipped cream or ice cream.