Spray an 8 x 8 inch cake pan with non-stick spray. Preheat oven to 350 degrees.
Pour bag of frozen blackberries onto a microwave safe plate; defrost for 1 minute. Pour fruit into baking pan.
Sprinkle lime juice and 1 tablespoon sugar over berries.
In a medium bowl, combine the 1 cup sugar, flour, and egg. It will be a crumbly mix.
Distribute the mixture evenly over the fruit.
Melt 5 ½ Tablespoons of butter and drizzle over mixture.
Bake for 20 - 25 minutes, checking to ensure bubbling fruit and a golden-brown top. Remove from oven and allow to cool for a few minutes before serving warm with ice cream (optional but highly recommended)