VARIATION: To make another version of green salsa that's typical of street stands, blend the avocado with the onion and cilantro. Then taste for lime juice and salt, and blend again. COOKING TIP: As with every salsa in Mexico, it's really the cook's touch that gives it personality. Feel free to add more water if you want it thinner, and-even though some Mexicans probably wouldn't agree-you can even omit the salt, which creates a brighter, sweeter salsa that's almost like a relish. If you own a powerful blender, no need to chop anything first. Just toss it in the blender jar whole.