Fill a jar with ice.
Stir in the tequila, allulose, and stevia.
Note: The allulose nutrition facts may list it as a carbohydrate. It is not a sugar and net carbs should be calculated by subtracting allulose content, similar to sugar alcohols.
Run a lime wedge around the rim of a margarita glass and dip in salt.
Fill the margarita glass with ice.
Strain cocktail over the glass and garnish with a lime wedge.