In a small saucepan, bring the broth to a boil. Remove from heat. Place the sun-dried tomatoes in the broth 15 minutes, or until softened. Drain, reserving broth, and coarsely chop.
Bring a large pot of lightly salted water to a boil. Place penne pasta in the pot, cook 9 to 12 minutes, until al dente, and drain.
Place the pine nuts in a skillet over medium heat. Cook and stir until lightly toasted.
Heat the olive oil and red pepper flakes in a skillet over medium heat, and saute the garlic 1 minute, until tender. Mix in the spinach, and cook until almost wilted. Pour in the reserved broth, and stir in the chopped sun-dried tomatoes. Continue cooking
2 minutes, or until heated through.
In a large bowl, toss the cooked pasta with the spinach and tomato mixture and pine nuts. Serve with Parmesan cheese.