Preheat oven to 450°F with a rack in the center. Finely chop 2 plum tomatoes. Finely chop 1 teaspoon of garlic. Finely chop ¼ oz fresh cilantro stems, keeping leaves whole. In a small bowl, combine tomatoes, cilantro stems, and ½ teaspoon each of garlic, vinegar, and oil. Season to taste with salt and pepper. Set salsa and whole cilantro leaves aside until step 6.

Heat 2 teaspoons oil in a medium skillet over medium-high. Add 10 oz pkg grass-fed ground beef and remaining garlic; season with salt and pepper. Cook, breaking beef up into smaller pieces, until deeply browned and meat is cooked through, about 6 minutes. Carefully spoon off any excess fat.

To the skillet with beef, add 15 oz can black beans and their liquid and 1 teaspoon chipotle chili powder (more or less, depending on your heat preference). Cook, stirring occasionally, until liquid is reduced by half and beans are warm, 5-6 minutes. Remove from heat. Season to taste with salt and pepper. Cover to keep warm.

Arrange 6 (6-inch) corn tortillas on a rimmed baking sheet. Drizzle oil generously with oil on both sides, then sprinkle with salt. Bake on center oven rack until crisp and lightly browned in spots, flipping tortillas halfway through baking, 8-10 minutes (watch closely as ovens vary). Remove from oven.

Divide beef filling among toasted tortillas and top with 2 oz shredded cheddar-jack blend. Return baking sheet to center oven rack and bake until cheese is melted, about 3 minutes.

In a small bowl, slightly thin all of the 2 (1 oz) sour cream by stirring in 1 teaspoon water as needed; season to taste with salt and pepper. Halve radishes, then thinly slice. Just before serving, garnish tostadas with sour cream, salsa, radishes, and whole cilantro leaves. Enjoy!