There are various ways to present this shooter. You can coat a lemon slice and lay it over the surface of the glass to bite into after the shot, or you can take it one step further and soak the lemon in Cointreau before coating it, then ignite!
1 oz lemon vodka
1/3 oz Cointreau
1/3 oz fresh lemon juice
1 lemon slice
Add all the ingredients to a shaker filled with ice. Shake very hard and strain into a shot glass. Garnish with a lemon slice.