In a food processor, pulse bake mix, sugar substitute and salt for 5 seconds, just to combine. Add butter and pulse until mixture resembles a coarse meal, about 30 seconds. Place this in a large mixing bowl and toss with blueberries and lemon zest.

In a large liquid measuring cup or small bowl, whisk heavy cream, sour cream and egg until well-mixed. Pour over dry mixture and stir with a fork just until just-combined. Chill the dough for 30 minutes.

Preheat oven to 375º F. Separate dough into 10 equal-sized balls and pat each piece into a disk measuring 2 ½” to 3” across. Space disks evenly on an ungreased baking sheet, leaving one inch between each scone.

Bake scones for about 25 minutes, until bottoms are golden brown and tops are light golden. Cool on baking sheet set on a wire rack.