Slice the 4 tomates verdes grandes firmes y sin madurar, aproximadamente rodajas de 1/4-inch into 1/4-inch thick rounds. Lay them out on a Wire Rack set over a Baking Sheet and sprinkle both sides generously with 1 tsp 1 tsp sal kosher para salar tomates. Let them sit for 10 minutes — this draws out excess moisture and helps the coating stick.

Set up a 3-stage breading station using shallow bowls. Mixing Bowl 1: Whisk together 1/2 cup ½ cup harina para todo uso, 1/2 tsp 1 tsp sal kosher para salar tomates, and 1/4 tsp 1 tsp sal kosher para salar tomates. Bowl 2: whisk together the 2 huevos and ¼ cup suero de leche until smooth. Bowl 3: stir together the ¾ cup harina de maíz amarilla molida fina o media, 1/4 cup ½ cup harina para todo uso, 1 tsp polvo de ajo, 1 tsp pimentón, ½ tsp pimienta de cayena (if using), and 1/2 tsp 1 tsp sal kosher para salar tomates.

Pat the 4 tomates verdes grandes firmes y sin madurar, aproximadamente rodajas de 1/4-inch slices dry with paper towels — removing that surface moisture is the key to a crispy, non-soggy crust. Working one slice at a time, dredge in the seasoned ½ cup harina para todo uso (shake off excess), dip in the 2 huevos-0.25 cup suero de leche mixture (let the excess drip off), then press firmly into the ¾ cup harina de maíz amarilla molida fina o media mixture, coating both sides evenly. Set the breaded slices on the Wire Rack.

Heat the ½ cup aceite vegetal in a large Cast Iron Skillet over medium-high heat until it reaches 350°F. You can test readiness by dropping a pinch of ¾ cup harina de maíz amarilla molida fina o media into the oil — it should sizzle immediately and steadily.

Working in batches of 3–4 slices (do not crowd the pan), carefully lower the breaded 4 tomates verdes grandes firmes y sin madurar, aproximadamente rodajas de 1/4-inch into the hot ½ cup aceite vegetal. Fry for 3–4 minutes per side, until deeply golden brown and crispy. Adjust heat as needed to maintain a steady sizzle — too hot and the crust burns before the tomato softens; too cool and the crust absorbs oil.

Transfer the fried 4 tomates verdes grandes firmes y sin madurar, aproximadamente rodajas de 1/4-inch to the Wire Rack (not paper towels — a rack keeps the bottom crispy). Sprinkle with a pinch of 1 tsp sal kosher para salar tomates immediately while still hot. Repeat with remaining slices, adding a splash more ½ cup aceite vegetal between batches if needed.

For a simple dipping sauce, stir together the ½ cup crema agria and 2 tbsp salsa picante como Tabasco o Crystal. Arrange the fried 4 tomates verdes grandes firmes y sin madurar, aproximadamente rodajas de 1/4-inch on a platter, garnish with 2 tbsp cebollino fresco cortado en rodajas finas, and serve immediately with the dipping sauce on the side. They're best eaten right away while the crust is at peak crunch.