I found this recipe on the Container Store website - of all places! It's on the webpage of the bottle that they sell (pictured below) that can be used to store the lemon vodka.

No Cooking Required
One of the easiest, prettiest gift recipes we've found. Lemon peel gives the vodka a pale yellow color and just a hint of citrus flavor.

Quantity: 1 quart

Storing: Store in a cool, dry place.

Ingredients
1 quart vodka
1 lemon

Instructions
Peel lemon in a long spiral, about 1/4" wide, using a sharp knife. Avoid the white pith underneath the peel; it will make the vodka bitter. Decant vodka into decorative bottle. Insert lemon spiral, cork or cap tightly and steep at least 1 week to let the flavor develop.

Hot Chili Pepper Variation
For Hot Chili Pepper Vodka, crush 2 small dried hot chili peppers and add to vodka along with 4 whole dried peppers. Cover and store in a cool place for 1 week. Strain the vodka through a fine sieve and pour into a decorative bottle. Cork or cap tightly.