Place the blackberries, sugar, and water in a blender and blend on high speed until combined.

In a medium saucepan combine blackberry puree mixture. Bring to a boil over medium/high heat. Reduce the heat to low and simmer until the sugar has dissolved, about 8-10 minutes. Skim the foam that has risen to the surface and discard. Remove mixture from heat and add a splash of vanilla extract.

Place the syrup, plus 1 cup of blackberries in a blender and blend until smooth. Strain the mixture to remove the blackberry seeds. Discard the seeds.

To a large glass container or a pitcher - Add the blackberry puree, freshly squeezed lemon juice, and cold water. Stir the mixture until fully combined.

Taste and adjust the sweetness as desired.

To serve: Add ice to an 8 oz glass. Fill the glass halfway with blackberry lemonade and top with seltzer.

Makes about one half gallon.