Using a food processor, puree the pears until smooth.

In a medium saucepot, combine the pureed pears, diced pineapple, orange juice, lemon juice, and lemon zest. Stir until well combined and heat to roiling boil on high heat, stirring occasionally.

Once mixture begins to boil, reduce heat to medium-low, add sugar and stir until well combined.

Simmer at medium/medium-low until mixture reaches 220°F (~1 hour), stirring every 8-10 minutes.

Once mixture reaches 220°F, allow it to boil for another 2-3 minutes, stirring constantly. (Note: The marmalade should be fairly thick at this point. If it drips off of a wooden spoon easily, then allow it to cook for several more minutes while you stir it constantly.)

Remove marmalade from heat and let cool at room temperature. Once fully cooled, store in air-tight container in refrigerator for up to 3 weeks.