Combine boiling water and sun-dried tomatoes; cover and let stand 15 minutes or until soft. Drain tomatoes in a colander over a bowl, reserving 3/4 cup liquid. Combine tomatoes, reserved liquid, olives, basil, lemon juice, and garlic in a blender or food processor; process until smooth. Place tomato mixture in a small bowl; stir in oil. Cover and chill.
Preheat oven to 350°.
Place half of bread slices on a baking sheet coated with cooking spray. Lightly coat bread slices with cooking spray. Bake at 350° for 4 minutes. Turn bread slices over; lightly coat with cooking spray. Bake an additional 4 minutes. Repeat with remaining bread slices. Cool completely.
Garnish tapenade with parsley, if desired; serve with crostini.