Preheat the oven to 375°F/190°C.
Place sliced tomatoes and zucchini on a large baking sheet in a single layer. Drizzle a teaspoon of olive oil over vegetables and sprinkle with salt and pepper. Bake for 25 minutes, flipping zucchini and rotating pan halfway through.
While zucchini and tomatoes are roasting, rinse quinoa in fine-mesh strainer under cold running water, and place in medium-sized pot. Add vegetable broth and 1 cup of water, then bring to boil over high heat.
Once boiling, reduce the heat to low, cover, and simmer for 15 minutes. Pour cooked quinoa into a medium-sized mixing bowl and fluff with a fork.
While quinoa is cooking, roughly chop kale. Pour remaining 2 teaspoons of olive oil into a small saucepan over medium-low heat. Once oil is hot, add chopped kale to the pan and sprinkle with salt and pepper. Cook until kale has softened, stirring occasionally, about 3 minutes. Set aside.
After roasted vegetables are cool enough to handle, chop zucchini slices into quarters. Add roasted vegetables and sauteed kale to the mixing bowl with the quinoa. Add lemon juice to the quinoa mixture and add feta cheese (optional).
Stir well to combine. Add extra salt and pepper to taste.