Pour ½ cup of cold water into a mixing bowl, sprinkle gelatin over it, and let it bloom for 5 minutes without stirring.
Pour 1½ cups of boiling water over the bloomed gelatin and whisk vigorously for 2-3 minutes until completely clear.
Add 1 cup of juice, 2 tablespoons of lemon juice, sweetener, and salt, whisking until combined. Add optional boosters if desired.
Let the mixture cool for 10 minutes, then pour into molds or a dish. Refrigerate for at least 4 hours or overnight.
Unmold or slice the jello and store leftovers in an airtight container in the refrigerator for up to 5 days.