Torta Rustica

1. In a large bowl, combine yeast and 1/4 cup (60 ml) warm water. Stir until dissolved. Stir in 1 cup (230 ml) warm water, melted margarine, salt (if using), and sugar. Gradually stir in 2 1/2 cups (350 g) flour, blending until dough is smooth and elastic. Sprinkle half of remaining flour onto a board. Turn out dough and knead dough until smooth and elastic, adding rest of flour as needed.
2. Place dough in a large bowl sprayed with cooking spray. Turn dough to coat all sides. Place bowl in a large white plastic trash bag. Close with tie and set on kitchen counter for 30 to 40 minutes to allow dough to rise, until doubled.
3. Punch dough down, squeezing out air bubbles. Shape into a smooth ball. With a sharp knife, divide dough into 2 equal portions. On flour board, roll out one portion to a 9-inch (23 cm) round. Place in a 9- by 1 1/2 -inch (23 by 24 cm) cake pan which has been lightly sprayed with cooking spray.
4. Meanwhile, remove casings from turkey sausage. Coarsely chop and sauté over medium-low heat until sausage is browned. Drain sausage well on paper towels. Place sausage on bread round. Arrange onion and tomato slices over sausage. Sprinkle with herbs. Top with mozzarella and Parmesan cheese.
5. Preheat oven to 350°F (180°C), Gas Mark 4. Adjust oven rack to lowest position. Roll out second portion of dough into a 9-inch (23 cm) square. Cut into 1-inch (2.5 cm) strips. Weave strips over filling in a lattice pattern, tucking ends of dough down around filling at the pan rim.
6. Bake for 35 to 40 minutes or until torta is richly browned. Cool in pan for 5 minutes. Loosen edges with a sharp knife. Remove from pan; cool on a wire rack. Serve warm or at room temperature. When ready to serve, slice into 8 wedges.