Preheat oven to 400°F and line a baking sheet with parchment paper. Add the tomatoes, onion, and corn along with high heat oil, salt, pepper and garlic powder. Mix until evenly coated then spread out on the pan. Bake in the oven for about 20 minutes, until chickpeas are slightly crispy and tomatoes are soft. Meanwhile prepare the dressing by combining the all of the ingredients listed into a food processor. Blend until smooth. Alternatively you can finely chop the basil by hand and mix in a small bowl.Place the chopped romaine and baby spinach in a large bowl and top with diced avocado. Remove the vegetables from the oven and allow to cool for a few minutes before dividing on top of each salad. Drizzle the lemon-basil yogurt dressing on top and enjoy!