Slice the angel food cake in half horizontally. Remove a tunnel from the bottom half, making sure not to cut all the way through the bottom of the cake.
Add the berries, lemon juice, sugar & vanilla extract to a saucepan. Cook for 10-15 minutes or until berries are macerated & sugar is dissolved. Remove from heat to cool.
Drain the berries, reserving the liquid.
Add the cooled berries to the tunnel in the bottom layer of the cake. Add the top of the cake back onto the bottom half.
Return the berry liquid to a small saucepan. Dissolve cornstarch into 2 tablespoons of water; whisk it into the berry liquid. Simmer on low until bubbly & thickened, about 5 minutes. Remove from heat. Cool slightly.
Pour the glaze onto the cake evenly so that it runs down the sides & looks pretty. Slice & devour!
