Make the Dough
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy (about 2-3 minutes).
Add eggs and vanilla extract; mix until combined.
In a separate bowl, whisk together flour, baking soda, salt, and cream of tartar. Gradually add the dry ingredients to the wet, mixing until a soft dough forms.

Chill the Dough
Divide dough in half. Shape into rectangles, wrap in plastic, and refrigerate for at least 1 hour (or freeze for 30 mins) for easier rolling.

Prepare the Filling
Mix the softened butter, brown sugar, and cinnamon into a thick paste.

Roll & Fill
On a floured surface, roll out one dough portion into a rectangle (about ¼-inch thick). Spread half of the filling evenly across the surface.
Starting from the long edge, tightly roll the dough into a log. Repeat with the second half of the dough and filling. Wrap both logs in plastic and refrigerate again for 1 hour (or freeze 20–30 mins) until firm.

Slice & Bake
Preheat oven to 350°F (175°C). Line baking sheets with parchment.
Mix the rolling sugar and cinnamon in a small bowl.
Slice chilled dough into ¼ to ⅓ inch rounds. Roll edges in cinnamon sugar mix, then place 2 inches apart on baking sheets.
Bake for 10–12 minutes, until just set and slightly golden on edges. Let cool 5 mins on pan, then transfer to wire racks.