Flank Steak with Balsamic Roasted Eggplant

Name: Flank Steak with Balsamic Roasted Eggplant
Ingredients: 2 eggplants (10 to 12 ounces each), cut into 3/4-inch cubes; 1 red onion, cut into 1/4-inch-thick wedges; 5 tablespoons extra-virgin olive oil; Kosher salt; 1/2 teaspoon red pepper flakes; 3 tablespoons balsamic vinegar; 1/2 cup oil-packed sun-dried tomatoes, drained; 1 clove garlic, smashed and peeled; 2 teaspoons fresh lemon juice; 1 1 1/4-pound flank steak, halved lengthwise then crosswise; Freshly ground pepper; 2 teaspoons herbes de Provence; 1 cup torn fresh basil