Taco seasoning is a spice blend containing all the spices you need for authentic-tasting tacos. It is a great option to have on hand for quick and easy weekday meals. It is also easy to find in the US as a large number of grocery stores carry some version of it. If you do not have any taco seasoning in your spice cabinet, replacing it will still be fairly easy. Consider the following options.
Your best bet: Make your own taco seasoning
Taco seasoning was invented for convenience. It provided a standardized formula made for home cooks so that they would not have to measure out ingredients individually, but could simply grab a single jar and add authentic Mexican spices to their taco filling. However, it’s not too difficult to whip up your own blend if you are familiar with the spices that are used to make taco seasoning and have them on hand. You can even modify the ingredients to suit your taste the way a Mexican cook would. You will need cumin, red chili pepper, and a few other ingredients including garlic. Garlic will help to make up the background flavor note. Most versions sold in stores contain salt as well. It is a good idea to use tomato powder to get a more accurate imitation of taco seasoning’s flavor and color. See a spicy taco seasoning recipe here from PepperScale.
A decent second choice: Chili powder
In the early part of the 19th century, chili was a popular dish in Texas. This dish was influenced by Mexican cuisine held a special place in the hearts of many Texans. Chili powder was invented by a Texan named Willi Gebhardt as an easy way for home cooks in the US to utilize the flavors of traditional Mexican spices. Prior to the invention of chili powder, it would have been necessary to procure the individual spices in order to cook chili. This would have been no small task in the rural parts of 19th century Texas. Among the ingredients were cumin and oregano along with a base of dried and ground chili peppers. These ingredients are all found in taco seasoning, and this is what makes chili powder an excellent taco seasoning substitute.
Remember that some blends of taco seasoning include tomato powder to provide some acidity and to give the taco meat a red color. In order to replicate this, you can add tomato powder separately or use tomato paste elsewhere in the recipe. Tomato paste should provide the same flavor and color benefits without making the taco meat too watery.
In a pinch: Fajita seasoning
Fajitas are tacos filled with grilled meat, as opposed to the braised ground meat that is the usual taco filling. Fajita seasoning is another convenient seasoning for Tex-Mex food and provides traditional flavors. It contains many of the same ingredients as taco seasoning and which are almost universal throughout Tejano and Mexican cuisine. Those ingredients include chili peppers and cumin; however, there is a crucial twist in the form of acidity. Most pre-made fajita seasonings will have an acidic note that is meant to be similar to the flavor of sour citrus, which often used to flavor fajitas. Citric acid is often used to provide that sour note. Keep in mind that the sourness may go well with the standard taco filling, but may not play well with all ingredients or suit all palates.
Combining these two spices: chili powder and cumin can provide you with much of the flavor profile that you want from taco seasoning.