In a pint glass or cocktail shaker, add ice, gin and vermouth. Allow them to sit, without shaking or stirring, for 2-3 minutes. You can swirl it a few times if you want.
If you are zesting the lemon, do it right over the martini glass.
Strain the martini into a chilled martini glass, give the lemon zest a twist over the glass and add it to the drink.
Serve right away to your adoring fans.
Notes
This is a very strong drink. If you are a lightweight, you may want to share it. You can also make this with 2 ounces of gin if you prefer.