Begin by washing 2 medium-sized zucchini under cold water. Slice them into even half-moon pieces, about ¼ inch thick, ensuring uniform cooking. Set the prepared zucchini aside in a bowl.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Once the oil shimmers, add diced onions and, if using, diced poblano pepper. Sauté for 5 minutes, stirring occasionally until the onions become translucent.

Create a space in the skillet by pushing the sautéed onions aside, and add 1 teaspoon of garlic powder. Sauté for about 15 seconds until fragrant, then incorporate 1 cup of diced fresh tomatoes, mixing everything together.

Add the prepped zucchini and 1 cup of corn to the skillet. Sprinkle with 1 teaspoon of cumin, and season generously with salt and pepper. Toss everything together to coat the vegetables evenly.

Reduce the heat to low and cover the skillet with a lid. Let the mixture simmer uncovered for about 6-8 minutes, stirring occasionally.

Preheat your broiler. Carefully transfer the zucchini and corn mixture to a baking sheet. Broil for 2-3 minutes, watching closely for golden bits and slight charring.

Remove the baking sheet from the oven and let the Calabacitas cool for a minute. Transfer the dish to a serving bowl and garnish with freshly chopped cilantro.