can I substitute a sugar substitute like Splenda (for baking) or do we need the caramelization you get from real sugar?

Agree … Splenda will not caramelize and also I think it would end up tasting “off”. It’s not a whole lot of sugar in the recipe and you’re not eating a whole lot of jam at once so I’d recommend following the recipe as written.

Hi! I haven't tried a sugar substitute in this recipe (or worked with Splenda much), so I'd recommend sticking with granulated.