Place shredded cheese, onion, mayonnaise and cayenne pepper in large bowl. Stir until well combined. Place 3-inch custard cup upside down in middle of 10-inch spring form pan.
Sprinkle half the pecans in bottom of pan. Spread cheese mixture on top of pecans. Cover with plastic wrap and chill mixture until firm, at least 1 hour.
When ready to serve, unmold cheese ring onto platter and pat remaining pecans onto top and sides of ring. If desired, spoon strawberry preserves in center. Serve with crackers.