Purée cherries in a blender and pour into a medium saucepan over high heat. Add sugar, bourbon, and cornstarch. Whisk ingredients together and bring to a simmer. Reduce heat to medium-low and cooker, stirring occasionally, for 35-40 minutes, or until mixture is thick and coats the back of a spoon/spatula. (Mixture will also thicken as it cools.) Remove from heat and stir in vanilla.
Let filling cool and store covered in the refrigerator until ready to use.
To make the cake:
Preheat oven to 350°F. Line two 8-inch cake pans with parchment paper and spray with nonstick spray.
Whisk together cake flour, baking powder, and salt. Set aside.
In a large bowl, combine sugar, eggs, oil, and vanilla bean paste. Mix on medium speed with an electric mixer until just blended.
Add half of milk and half of flour mixture to the wet ingredients. Mix until just combined. Repeat with remaining milk and flour mixture. Mix well.
Divide batter evenly between cake pans. Bake for 23-25 minutes or until cakes are golden brown and set in the center. (Test by inserting a toothpick into the center of each cake layer. If it comes out clean, they're done!)
Let cakes cool in pans for about 5 minutes before transferring to a wire rack to cool completely.
To make the bourbon soak:
Whisk bourbon and powdered sugar together in a small bowl and use a pastry brush to brush mixture over the top of each cake layer.
To make the frosting:
Cream butter on medium-high speed with an electric mixer. With mixer running, add shortening. Mix until smooth and creamy.
Add bourbon cherry filling, half of the powdered sugar, and 1 tablespoon of cream. Mix until well blended. Repeat with second half of powdered sugar and cream, and mix for 1 minute.
When cake layers are cool, use a cake saw or serrated knife to cut off the dome and make an even layer. Place one cake layer on a plate or cake stand.
Transfer frosting to a piping bag with the tip cut off, and pipe a border around the top of the cake layer.
Spoon bourbon cherry filling over the cake and spread with a spoon.
Place the second cake layer on top and pipe or spread frosting all over the outside of the cake. Decorate as you wish! Garnish with fresh cherries if desired.
Store cake in the refrigerator until ready to serve.