Bec d’Asan (Emilia-Romagna-Style Eel Stew) | Saveur

Ingredients

• ¼ cups extra-virgin olive oil
• 2 medium yellow onions, thinly sliced (4½ cups)
• ¼ cups plus 1 Tbsp. tomato paste
• 1 cup white wine vinegar
• 2–2½ lb. eel fillets, cut crosswise into 3-in. pieces
• Kosher salt and freshly ground black pepper
• 3 tbsp. extra-virgin olive oil, divided
• 1 tsp. kosher salt
• ¾ cups (6 oz.) medium-grain polenta
• ¼ cups (2 oz.) finely ground buckwheat