1 ½cupsour creamor substitute by putting 1 tbsp white vinegar in a cup then filling the rest up with milk; let stand 5 minutes until thickened
1 ½cupsboiling water
Preheat oven to 350ºF. Grease and flour two 9x2" round cake pans, and line bottoms with circles of parchment paper. Set aside.
Add add flour, sugar, baking powder, baking soda and salt to the bowl of a standing mixer fitted with the paddle/beater attachment; beat with speed on low to combine.
In a separate bowl, whisk together eggs, sour cream, butter and vanilla extract. Add to flour mixture and beat until fully incorporated. Reduce mixer speed to low and carefully pour in boiling water. Beat until well incorporated, pausing to scrape down sides and bottom of mixer.
Divide batter between the two prepared baking pans and bake for about 45 minutes, or until top is springy. Cool completely on wire racks before filling and frosting.