Using a small saucepan, combine the sugar and water. Heat just until sugar has dissolved. Pour into a bowl, add the mashed berries and allow to cool.
Force the mashed berries through a fine sieve to remove as many seeds as possible.
Combine the berries, lemon juice, tequila and Grand Marnier in a pitcher. Chill in fridge at least 2 hours.
Pour sea salt into a small plate.
Rub the rims of each martini glass with the lemon wedge.
Dip and twirl the rim of each glass in the sea salt.
Pour 2 cups of the margaritas into a cocktail shaker filled with ice, reserving the rest of the margaritas for refills. Shake for 30 seconds, strain and pour into prepared glasses.
Recipe by Liz The Chef at https://lizthechef.com/fresh-raspberry-margaritas/