They make their tortillas in-house, seconds before they serve them to you. Jessica Stein

On a recent trip to Hillcrest Market, a mini-mart at Summit Avenue East and Olive Way, I noticed something I hadn't noticed before: the sound of sizzling. In one corner, a taco stand had materialized overnight.

A whiteboard listed four taco options: al pastor (pork), asada (steak), campechano (chorizo and steak), and veggie (potato and cactus). They were $2.50 each. What the hell, I was hungry. Sweet mother of Mary, they were some of the best tacos I'd ever had.

I've since taken lots of friends, and it's always a hit. Because there is no sign for the restaurant that you can see while you eat, I started calling the place Rock 'n' Roll Tacos, after a sign advertising wine that hangs over the booze section of the store. It says, in small letters, "Washington Wine Is Soooo...." And then in huge letters: "Rock 'n' Roll."

It's a fitting nickname, because these tacos rock. First of all, the tortillas are made in-house. While you eat, you can watch as they prep the next batch: Scoops of masa get flattened, one by one, followed by 10 seconds on the grill. "We make sure that it's crispy. It should be crispy," Miguel Cruz, 33, said of the tortillas when I stopped in again the other day.

This time, I noticed a small "Carmelo's Tacos" sign above the register. When I asked if he was Carmelo, Cruz said, "Carmelo is my father." He said they get their masa delivered "early in the morning, and sometimes it's still warm, because they cooked the corn so recently. You can touch it, and it's like—wow, that's fresh."

Carmelo Gaspar, 60, worked for Cactus restaurants for 27 years as a prep cook. This is his first business. The whole family is helping. "The asada that we serve you guys is the same asada that we do at home."

Regarding the al pastor, Cruz said, "That recipe has about 15 different ingredients." The meat is marinated overnight in guajillo chilies, ancho chilies, chipotle chilies, cloves, and pineapple juice, and then it's served (like all tacos here) with a bright-orange salsa roja (tomatoes, guajillo chilies, chile de arbol, roasted garlic) and a salsa verde with avocado ("You don't get it every time, but when you get it, you get chunks of avocado"). Plus, of course, diced pineapple.

"That was my idea," Cruz said about dicing the pineapple. "When I go to Tacos Chukis"—right up the street—"you take one bite, and the whole thing comes out," referring to the one big slice of grilled pineapple Chukis gives you. "Or you have to take it with your fingers and break it up yourself. So why don't we just cut it up for you?"

Chukis doesn't make their own tortillas. Theirs are soft, uncrispy, and out of a bag.

When I asked about the cactus in the veggie tacos, Cruz said, "The cactus? That's Mexico City." The family is from just south of there. The pickled veggies that come on the side of each plate of tacos are his auntie's recipe.

When I confessed to Cruz that I've been calling the place Rock 'n' Roll Tacos, he joked he was going to have to ask the mini-mart to take down that sign. Then he showed me pictures of the new Carmelo's Tacos sign they will be installing any day now.