First, trim as much fat as you can from meat. Place in a slow cooker.
In a blender, add about 1 cup of water. Blend cilantro, garlic (i usually use all of the bulb), onion, salt and pepper with water. (you can use as much or as little spices you want, depending on your taste).
Pour this mixture over meat then add about 2-3 cups of more water depending on how much meat you are cooking.
Cook meat in slow cooker on low for about 8 -10 hours. Again, this depends on how much meat you have.
If you are going to eat this for breakfast (which is the traditional way), cook the day before and let is cool overnight. (I usually start cooking mine on Saturday AM until about 6PM, then let it cool. When cool enough, I refrigerate overnight).
In the morning (Sunday AM) BEFORE heating up, skim all the grease that comes to the top.
CHEEK MEAT: Beef cheek meat is very tender but very very fatty. You may want to buy more or less meat, depending on the size. You can use beef roast, if you want, but cheek meat is AWESOME (if you can find it).