Roasted Eggplant and Bell Pepper Sandwich With Garlic Aioli

medium eggplant, sliced into 1/2-inch-thick rounds

red bell pepper, sliced into 1/2-inch strips

olive oil

smoked paprika

Kosher salt

Freshly ground black pepper

mayonnaise, or Vegenaise

garlic clove, minced

sherry vinegar

loaf of olive bread, sliced horizontally in 2-3 sections

red onion, sliced thinly

feta cheese, crumbled or sliced