Tortillas are the foundation of a great taco. You can spend hours roasting or braising meats and building complex salsas, but if the tortilla is mediocre, the best you can hope for is a mediocre taco. Freshness is critical, and there are many tortillerias and restaurants that make tortillas daily using Maseca, a product that looks like fine corn flour but is actually masa harina: dehydrated and powdered masa (corn dough made from boiled and soaked corn kernels). Traditionalists aren't content with Maseca though because the flavor is bland and the texture isn't as toothsome or pliable as tortillas made from fresh masa.
Nixtamalization is the complex process of using lime powder (the mineral, not the citrus fruit) to help turn hard field corn into a soft, malleable dough (see our complete story on nixtamal tortillas for details), the way it's been done for centuries in Mexico. Even in Mexico, most tortillas these days are made with Maseca, but you'll recognize the full-bodied, earthy smell of real corn tortillas as soon as you walk into a taqueria or cantina using nixtamal tortillas.
Not sure where to start? Boulder isn't known as a hotbed of authentic Mexican cuisine, but there's a surprising amount of nixtamalization happening there. Outside of restaurants, look for Bolder Tortillas at Boulder County farmers' markets and grocery stores, inluding Lucky’s Market, Natural Grocers, Alfalfa’s, Whole Foods, Cured, Fresh Thymes, Niwot Market, Mountain Fountain and Isabelle Farms. The blue corn product, made from whole corn kernels that have been cooked, soaked, rinsed and ground into masa before being pressed and fried into chips, can also be found at several Denver farmers' market. And Bolder Tortillas sells vacuum-sealed, partially cooked tortillas that you can take home and finish on a hot griddle or grill for a fresh taco experience.
For restaurants, T/ACO (1175 Walnut Street) makes nixtamal tortillas from scratch daily. Managing partner/owner Peter Waters says the restaurant has its own wet mill for grinding corn. "We actually use field dent corn, boil it with calcium lime and then steep it for a few hours," Waters explains. "We then feed it in to our own electric wet mill to make fresh masa, which we roll out into tortillas and cook on the flat top grill."
T/ACO makes enough masa every day that it sells some to other Boulder restaurants, including Arcana, Santo and River and Woods. At Santo (1265 Alpine Avenue), chef/owner Hosea Rosenberg uses fresh masa from T/ACO to make sopes and occasional daily specials like gorditas.
The restaurant, which takes its inspiration from Rosenberg's New Mexico roots, get its tortillas from Abbondanza Organic Seeds and Produce, which makes yellow, blue and rare green corn tortillas from heirloom corn varieties that were brought from Chihuahua, Mexico and are now grown in Colorado. Those tortillas are made into tacos, enchiladas and tostadas at Santo, and are also served warm and unadulterated alongside entrees like the braised and wood-fired lamb neck.
In Denver, Garibaldi Mexican Bistro (with locations at 1043 Broadway and 3298 South Broadway), boasts a "Menu Azteca" with traditional dishes like blue corn tacos and tlayudas (made on enormous, thin corn tortillas that can only be made properly with fresh masa). While the restaurant doesn't grind its own corn, it buys fresh nixtamal tortillas from a tortilleria in, you guessed it, Boulder.