Preheat your oven to 350º F and prepare 3 cake pans with cake goop or your prefered cake release
Add in your flour, sugar, salt, baking powder, baking soda, and softened butter into the bowl of your stand mixer with the paddle attachment. Set aside.
Place half of your sour cream and your vegetable oil into a measuring cup. Give it a quick mix until the oil and sour cream are combined.
Add in your rose water and vanilla extract into your sour cream and oil mix. Set aside.
Place the remaining half of your sour cream into your egg whites and mix until combined.
Mix your dry ingredients in your stand mixer on low speed for 1-2 minutes, or until the texture looks like sand.
Take your oil and sour cream mixture, then stream it into your flour mixture while mixing on medium - low speed. Mix for 2 minutes or until the color is pale and the mixture is nice and fluffy.
Stream in your egg whites and sour cream mixture in 3 parts while mixing on low speed. Make sure to let each part mix for a couple seconds before adding in the rest.
Add in your crushed rose petals and mix on low just to combine.
Divide your batter into your 3 cake pans. (If making cupcakes add 1-2 spoonfuls of batter into each cupcake liner)
Bake for 35-40 minutes or until you can place a toothpick in the center and it comes out clean. (If you are making cupcakes bake for 15 minutes)