Preheat oven to 325°F. Grease and flour two 9-inch cake pans.
In a bowl, whisk together the flours, baking soda, baking powder and salt.
In another bowl, beat the sugar, oil, shortening, eggs, vanilla, lemon extract and zest until light and fluffy.
Alternate mixing the dry ingredients and buttermilk into the wet ingredients until just combined.
Mix the vinegar and hot lemon water together, then stir into the batter along with food coloring if using.
Divide batter evenly between pans. Bake 25-30 mins until centers are just set.
Let cakes cool in pans 10 mins, then transfer to a wire rack to cool completely.
For frosting, beat cream cheese and butter until fluffy. Mix in extracts, zest and powdered sugar until smooth.
Frost cooled cake layers with lemon cream cheese frosting. Garnish with lemon slices if desired.