While any medium sized ripe zucchinis will do, use garden fresh ones if you have them. The tender sweet flesh of the zucchinis paired with the spiced meat and cool yogurt sauce will make you forget that this dish is less than 500 calories per serving!
Preheat the oven to 400˚ F. Drizzle a rimmed baking sheet with 2 tablespoons olive oil. Season the zucchini halves with salt and pepper. Add to the baking sheet and turn to coat with the oil. Arrange the zucchini cut-side down in a single layer. Roast until crisp-tender, about 15 minutes.
Meanwhile, heat the remaining 1 tablespoon olive oil in a large skillet over medium-high heat. Add the onion and cook until translucent, about 4 minutes. Stir in the cumin and 1/2 teaspoon each salt and pepper; cook 30 seconds. Add the turkey and cook, breaking it up with a wooden spoon, until browned, about 5 minutes. Stir in the tomato paste and chicken broth until combined. Cook until the broth is reduced to a thick sauce, 4 to 5 minutes.
Turn the zucchini boats cut-side up and fill with the turkey mixture, packing it in. Sprinkle with the cheese and roast until the zucchini is tender and the cheese is softened, about 10 minutes.
Meanwhile, stir together the yogurt and lemon juice; season with salt and pepper. Drizzle the zucchini boats with the yogurt mixture and top with the dill.