Lentil and Tomato Pie

INGREDIENTS

• 1 large onion
• 2 ounces butter or 2 ounces margarine
• 1 large garlic clove, crushed
• 6 ounces split red lentils, washed
• 12 fluid ounces unsalted stock or 12 fluid ounces water
• 2 Tomatoes, skinned and chopped
• 3 ounces grated cheese
• 1 teaspoon dried basil
• 1 tablespoon lemon juice
• 1 egg
• sea salt
• black pepper
• 8 ounces shortcrust pastry
• 1 beaten egg