Preheat the oven to 350 degrees F.
Grease a 9x13 cake pan (or 2 9-inch round pans) with baking spray and optionally line it with parchment paper.
Whisk together the flour, gelatin, baking powder, baking soda, and salt in a medium bowl. Set aside.
In a large bowl (or stand mixer), whip together the softened butter and sugar for about 4-5 minutes, until the mixture is pale yellow.
Add in the eggs one at a time, mixing well after each addition.
Scrape down the sides of the bowl. Mix in the oil, vanilla extract, and sour cream just until combined.
Gradually add in the flour mixture and milk, alternating one at a time, beginning and ending with the flour mixture. Mix well between each addition. Be careful not to overmix.
Pour the cake batter into the pan and spread to smooth.
Bake for about 25-28 minutes, or until the top begins to lightly brown and a toothpick comes out clean.
Place the cake on a wire cooling rack and allow the cake to cool completely before icing.