Cook pasta according to package directions, omitting salt and fat. Drain.
While pasta cooks, sprinkle shrimp with salt and pepper. Heat oil in a large nonstick skillet over medium-high heat. Add shallots; sauté 30 seconds. Add shrimp; sauté 3 minutes. Remove shrimp mixture from pan. Add chicken broth and lemon juice to pan, scraping pan to loosen browned bits. Add cooked pasta, shrimp, spinach, and capers, and heat 1 minute or until spinach wilts, stirring frequently.
Serve with ripe tomatoes dressed with oil and vinegar. Substitute finely chopped red onion if you don't have shallots on hand.