If desired, make rosemary simple syrup. Combine 1/2 cup water and 1/2 cup sugar (or 6 tbsp monk fruit sweetener) in a small pot. Bring to a boil for 1 minute, stir to dissolve sugar, then remove from heat, add 2 sprigs of rosemary and continue to steep for 30 minutes. Strain out rosemary sprigs and allow to cool.
If desired, moisten the rim of your serving glass with an orange slice, then dip into salt.
Add tequila, blood orange juice, and simple syrup to a shaker. Shake well, then pour over ice in your serving glass. Top off with ginger beer.
Garnish with a slice of blood orange and a sprig of rosemary.