Preheat your oven to 400°F and line a baking sheet with parchment paper.
Dice the eggplant, zucchini, and red bell pepper into uniform half-inch cubes.
Toss the cubed vegetables on the baking sheet with half of the olive oil and a pinch of sea salt, then roast for 20 minutes until tender.
Season the chicken breast evenly with the remaining sea salt, black pepper, and dried oregano.
Heat the remaining olive oil in a skillet over medium-high heat and sear the chicken for 6 to 7 minutes per side until fully cooked.
While the chicken rests, sauté the diced yellow onion and minced garlic in a small saucepan until they become translucent and fragrant.
Stir the tomato puree and the roasted vegetables into the saucepan, simmering on low heat for 5 minutes to allow the flavors to meld.
Slice the chicken breast into thin strips and serve it over a generous bed of the vegetable ratatouille.
Garnish the dish with fresh torn basil leaves before serving warm.