Step 1

Whisk together flour, salt,

Step 2

baking soda, cream of tartar,

Step 3

and 2 teaspoons cinnamon

Step 4

in a bowl. Beat butter, sweet potato

Step 5

puree, confectioners’ sugar,

Step 6

vanilla, and 1 cup granulated

Step 7

sugar on medium speed with

Step 8

an electric mixer until fluffy, 1 to 2 minutes. Add eggs,

Step 9

one at a time, beating until

Step 10

blended after each addition.

Step 11

Reduce speed to low and

Step 12

beat in flour mixture, just until

Step 13

flour is incorporated. Cover

Step 14

and chill at least 2 hours and

Step 15

up to 2 days. Preheat oven to 375 degrees F.

Step 16

Line two baking sheets with

Step 17

parchment paper. Stir

Step 18

together remaining 1 1/2 teaspoons cinnamon and 1/2 cup

Step 19

granulated sugar in a bowl.

Step 20

Roll dough into balls (about

Step 21

1 tablespoon each). Roll balls

Step 22

in cinnamon sugar, and

Step 23

arrange, 2" apart, on

Step 24

prepared baking sheets. Bake until just golden

Step 25

around bottom edges, 10 to

Step 26

12 minutes. Cool on baking

Step 27

sheets for 1 minute, then

Step 28

transfer to wire racks to cool

Step 29

completely. Spread dulce de leche

Step 30

on the flat side of half of the

Step 31

cookies, dividing evenly.

Step 32

Sandwich with remaining

Step 33

cookies.