UPDATE: Since many of you have asked about a weight measure for the 10 cups of tomatoes, as I've been canning the salsa the last few days, I've done a little experimenting/research. Basically, I've found it varies GREATLY depending on variety. When I used SIX pounds of garden tomatoes + Roma (the paste tomatoes probably only made up about 1/3 of the total), after taking the skins off, lightly crushing, and draining, the yield of tomatoes to use in this recipe was about 2 1/2 cups. When I used TWO pounds of only Roma/paste tomatoes, after taking the skins off, lightly crushing, and draining, the yield of tomatoes to use was a little over one cup. I tend to err on the side of over draining the tomatoes, if anything, so that makes a difference as well. For me, because I usually use paste tomatoes in this recipe, I would plan on around 18-20 pounds (give or take) of Roma/paste tomatoes to get the 10 cups for this recipe...and even more if using tomatoes with a higher water/lower flesh content.
As you will notice when we dive a little further into these recipes, Mexican food has a stunning range of somewhat special ingredients. From Masa Harina, the essential ingredient of corn over a wide array of chilies either fresh, dried or ground to Mexican oregano and tomatillos. Some of these may at first glance seem foreign and difficult to come by, but fear not we’ll discuss the individual ingredients as we go and they’ll be easier to come by than you think.