For raspberry simple syrup:

Combine sugar, water, and raspberries in a saucepan. Simmer over medium heat and use a spoon to lightly crush the raspberries until all sugar is dissolved, about 10 minutes.

Remove from heat, allow to cool, and strain. Store in a canning jar in fridge for up to one week.

To make raspberry tequila martini:

To a cocktail shaker filled with ice, add raspberry simple syrup, vermouth, and tequila blanco.

Shake vigorously for 10 seconds, strain into glass. Garnish with additional raspberries and serve.