Empty the can of tomatoes into a food processor or blender. Add 1/2 of the onion and cilantro, 1 pepper, juice of half the lime, 2 cloves of garlic, and 1 teaspoon salt. Pulse until combined and to the consistency you like. Take a chip and taste.

This is where you get to customize your salsa to your taste. If you adore cilantro, go ahead and add the rest of the bunch. Maybe your salsa needs more heat, so add another pepper. If it’s too tomato-y, put in in the rest of the onion and another clove of garlic. And always add more salt if needed.

Pulse again until blended.

As soon as you’ve got your salsa tasting delicious, add whey and pulse a couple more times. Transfer to a clean quart-size jar with lid. Leave to ferment on your counter for at least 12 hours, but not more than 24 hours. Burp the jar if necessary halfway through the fermenting time. Store in the fridge. Salsa will keep for 3 to 4 months, but ours is usually devoured in a couple of weeks!