My recipe uses just 7 ingredients. After much experimentation, I found that adding anything more or less only served to minimize the flavor. Those seven magical ingredients are:
If you don't plan on using your cilantro right away, you'll want to place it in a cup of water to keep it from wilting.
Get yourself a good food processor. There's no better way to make salsa. Tomatoes should be vine ripe if possible, preferably from your own garden. Nothing is more critical to good salsa than quality tomatoes. Cut in quarters and add FIRST. This is important, as it allows for the best blend. 3-5 tomatoes depending on size.
I like to let my cilantro sit in a large bowl of water for awhile. The sand and grit will sink to the bottom. Then I rinse it under cold water before drying it out in a salad spinner. After that, I pick out each and every badly wilted or slimy piece in the bunch. I'm a bit OCD about this. Finally, I chop the bunch into about 4-5 sections before adding. If you don't cut them up, the cilantro will wrap itself up around your blades. 1/3 to 1/2 bunch per batch.
This is where you can get a bit creative. I've tried many different variations of onions, but my favorite is simply yellow with green. In this particular instance, I've added white onions to the mix. I don't recommend using red ones. They overpower everything else. By adding them third, they do a good job of weighing down the cilantro. I generally go with the equivalent of 1 normal sized onion per batch, but that's usually made up of 2-3 varieties.
Jalapeno & Garlic
Jalapeno is all about temperature control. I like to add 1-2 per blended batch. I leave the seeds in for heat. I tried using other varieties of peppers, but I lost temperature consistency. Garlic should be freshly peeled with the rough end chopped off. You can vary the number of cloves you add depending on your affinity for garlic. I like 5-6 per batch.
Tomatoes & Salt
Yes, tomatoes again. You need another 1-2 tomatoes for the right ingredient ratio. By adding a top layer, you get a better blend. Go with Kosher salt. Regular table salt is gross. Kosher has a much stronger flavor and dissolves well. I never measure. Go with your gut.
Lime is key in the preservation process. Together with the salt, it will keep your salsa fresh in the fridge for weeks. (don't hold me to that though) Do not use lime concentrate from those lime shaped bottles. It's NOT the same thing. Freshly squeezed lime has a unique, delicious flavor that brings the salsa together. I like to cut a triangle wedge from each quarter, throw it in, and then squeeze the juice from the remaining quarter. You get more liquid that way. I use 1 whole lime for each batch.
Start with several pulses to get things going, then hold down until you get the consistency you like. I like mine a bit chunky, but still well blended.
This bowl represents 4 batches from my 10 cup food processor. It's a lot of salsa. Enough to feed a small army or service an entire cafeteria of grade schoolers. I finished it off in a couple weeks. My tolerance for salsa is very high. Put a lid on it and refrigerate. It tastes better after it's allowed to sit for a few hours.
Congratulations, you now have the best tasting salsa in the world. Donations gladly accepted.