Lamb Shanks with Roasted Tomatoes and Lentils

Ingredients (6 servings): ¼ cup extra virgin olive oil 6 lamb shanks, French trimmed 1 large brown onion, finely chopped 2 celery stalks, finely chopped 2 garlic cloves, crushed 1 litre chicken stock 1 cup dried French-style puy lentils (see notes) 200g cherry tomatoes, halved 2 teaspoons finely grated lemon rind 2 tablespoons lemon juice…