Instructions:
- Prepare the Gelatin (Bloom): In a heat-proof bowl, sprinkle the unflavored gelatin over the ½ cup of cold water. Let stand undisturbed for 5 minutes until softened and spongy (bloomed).
- Make the Cranberry Base: In a medium saucepan, combine cranberries, sugar, and ½ cup of water. Bring to a boil over medium heat, then reduce heat and simmer until most cranberries have burst (about 5-7 minutes). Stir frequently.
- Finish the Sauce: Remove the pan from heat. Stir in the orange zest and orange juice.
- Dissolve Gelatin: Pour the 2 cups of boiling water into the bowl with the bloomed gelatin. Whisk gently until the gelatin is completely dissolved and the liquid is clear.
- Combine Liquids: Gently stir the warm cranberry mixture into the dissolved gelatin mixture. Then, stir in the chilled lemon-lime soda.
- Fold in Fruit (Optional): Gently fold in the well-drained crushed pineapple, ensuring you don't introduce too many air bubbles.
- Set: Pour the entire mixture into a lightly oiled 9-inch loaf pan or 6-cup bundt pan.
- Chill: Cover loosely with plastic wrap and refrigerate for at least 4 hours, or until completely firm and set.
- Unmold & Serve: To serve, dip the bottom of the mold briefly (5-10 seconds) in hot water. Invert onto a serving platter. Slice with a sharp, warm knife.