Place the cashews in a bowl and cover them with the warm water. Let them soak together while you measure the rest of the ingredients, about 5 to 10 minutes.

Pour the cashews and their soaking water into the blender, then add in the olive oil, lemon juice, vinegar, salt, mustard, onion powder, garlic powder, and black pepper. Secure the lid on the blender and blend until smooth, about 60 seconds. Stop and scrape down the sides, as needed, to make sure everything gets blended, and add an additional tablespoon of water, if needed, to help the cashews break down into a silky-smooth texture.

Next, add in the parsley, chives, and dill, and pulse briefly, just to incorporate them. (This gives the dressing a speckled look, like traditional ranch. If you blend too long it could turn green instead.) Taste and adjust any seasoning as needed. You may want to add up to ¼ teaspoon more salt, or extra lemon for a more tangy flavor.

Pour the dressing into an airtight container, cover, and refrigerate for at least 30 minutes to let the flavors develop. It will thicken much more in the fridge overnight, so I recommend adding a tablespoon of water, or more, as needed to thin it out again the next day. Store in the refrigerator for up to 1 week. Shake the dressing before each use.