Preheat your oven to 350°F. Line two baking sheets with parchment paper and set aside.
Mix the baking soda and the sour cream in a large liquid measuring cup and set aside.
Whisk all your dry ingredients together in a large bowl. Add your butter and cut in until it's crumbly.
Take your lemon and grate the peel off of it into the flour mixture.
Cut your lemon in half, and squeeze all the juice out, picking out the seeds. You should get almost a 1/4 cup of lemon juice.
Add in enough milk to bring it to 1/3 of a cup. Don't worry if the milk curdles.
Mix the sour cream, milk, and egg into the dry ingredients. Once it's mixed a bit, add in the cranberries. Divide into three balls, then flatten into 6-inch wide disks. Cut each piece into 6 triangles.
Bake the scones until they are golden brown, from 18-23 minutes depending on your oven. The bottoms will be golden brown and the tops hard and crispy.
Remove and eat warm or cool.
Notes
This is a dry scone mixture, that's how they end up crispy and buttery. Keep mixing until the ingredients come together.