Step 1

In large bowl, whisk together flour, baking powder, and salt.

Step 2

In another large bowl, using electric mixer, beat butter and sugar until light and fluffy, about 3 minutes. Beat in thyme and 2 teaspoons lemon zest, then egg and vanilla.

Step 3

Reduce mixer speed to low and gradually add flour mixture, mixing just until incorporated. Shape dough into two 1 1/2-inch-diameter logs. Wrap between 2 sheets of waxed paper and freeze for 20 minutes.

Step 4

Heat oven to 350°F. Line baking sheets with parchment paper. Slice into 1/8-inch-thick rounds and place on prepared sheets.

Step 5

Bake, rotating positions of baking sheets halfway through, until cookies are light golden brown around edges, 10 to 12 minutes. Let cool on sheets 5 min. before transferring to wire racks to cool completely.

Step 6

In bowl, combine confectioners’ sugar, fresh lemon juice and remaining lemon zest. Spoon over cooled cookies. Sprinkle with additional thyme if desired.