I have tried the Warm Blondie Pudding recipe and it is delicious. I love its "pudding" texture and warmth and we ate the delightful dish, with spoons, served with creme fraiche as Nigella suggests. I wonder, though, if it is possible to add fruit of some kind ... perhaps apple, pear, or maybe figs ... even raisins? But, then again, perhaps this would upset the ratio of ingredients?
Nigella's Warm Blondie Pudding (from AT MY TABLE) is a gluten-free blondie that can be served warm as a dessert or baked slightly longer and then chilled and cut into bars. The batter includes roughly chopped walnuts and you could certainly switch the type of nut to pecans or hazelnuts if you prefer.
Adding fresh fruit to the batter will unfortunately change the way the blondie bakes, as the fruit will let out juice as it cooks and could make the blondie too soft or wet. Dried fruits are a possibility as long as you don't use too much. Dried cherries or cranberries may be an option as they are sweet-sharp and will not add to the overall sweetness of the blondie. And if you add dried fruits you may want to reduce the amount of walnuts, maybe using half nuts (50g/½ cup) and half dried fruits (50g/⅓ cup) instead.