Prep your gear: Set out a high-speed blender or food processor.
Have a loaf pan or shallow freezer-safe container ready.
Add ingredients: To the blender, add frozen raspberries, water, lemon juice, sweetener, and a pinch of salt. Add vanilla or a splash of alcohol if using.
Blend until smooth: Start on low, then increase speed. Stop and scrape the sides as needed.
If the mixture is too thick, add 1 tablespoon of water at a time until it blends smoothly.
Taste and adjust: Raspberries vary in tartness. Add another tablespoon of sweetener or a squeeze of lemon to balance. You’re aiming for bright and slightly sweet.
Strain if you want seed-free: Press the puree through a fine-mesh sieve into a bowl to remove seeds.
This step is optional but gives a silky texture.
Quick-freeze: Pour the mixture into your container. Freeze for 1–2 hours, stirring every 30 minutes to keep it scoopable. If you used alcohol, you may need a little less time.
Serve: Scoop into bowls.
If it firms up too much, let it sit at room temperature for 5–10 minutes before scooping.