Preheat the oven to 350°F. Line a baking sheet with parchment paper.

In a large mixing bowl, use a handheld mixer to cream together sugars and butter until fluffy and creamy. Mix in applesauce and vanilla. Add flour, baking soda, cream of tartar, and salt. Mix on low until a soft dough forms.

Form dough into a rough ball and place on top of a piece of parchment paper. Place another peice of parchment on top of dough. This will prevent the dough from sticking to the rolling pin. Roll dough into a 10x11" rectangle.

Make the cinnamon sugar filling by whisking together all ingredients until a paste forms. Spread filling into the middle third of the rectangle. Take the edges of the parchment paper along with the dough and roll into a tight log. Slightly flatten long and cut into ½" portions. Roll each portion into a smooth ball then place on the prepared baking sheet.

Bake for 10-11 minutes until middle is soft and edges are lightly brown (do not overbake!). Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire cooling rack.

Once cookies have cooled, drizzle with icing (1 cup powdered sugar + 2-3 tsp non-dairy milk).