Preheat the oven to 400 degrees F (200 degrees C).

Combine flour, sugar, baking soda, and lemon zest in a bowl. Cut in butter until the mixture resembles coarse crumbs. Fold dewberries in gently. Add 1/2 cup soy milk and stir to combine. Add just enough additional soy milk until dough leaves the sides of the bowl and forms a ball.

Place dough on a floured surface and knead about 10 times. Transfer dough to a parchment paper and spread into a 10-inch circle. Score the circle into 12 wedges and move parchment paper with dough onto a baking sheet.

Bake in the preheated oven until browned, 20 to 25 minutes. Serve warm.