Put the raspberries in a bowl and mash with a fork until broken up and turning juicy. Add the jam and mash together to make a purée. Tip into a sieve resting over a small bowl and press the purée with the back of a spoon to extract as much juice as possible.
Whisk the egg whites in a large clean bowl with a hand-held electric whisk until peaking. Whisk in a tablespoonful of the sugar and continue to whisk for about 15 seconds. Gradually add the remaining sugar, a spoonful at a time, until thick and glossy.
Drizzle over the raspberry purée and lightly stir in using a spatula or large metal spoon, scooping up the meringue from the base of the bowl so that the mixture is streaked with the purée. Take care not to over-mix.
Drop large spoonfuls of the mixture, each about the size of a small orange, on to a large baking sheet lined with baking parchment, then swirl with the back of a teaspoon. Bake in a preheated oven, 120°C (250°F), Gas Mark ½, for about 1¼ hours or until the meringues are crisp and come away easily from the paper. Leave to cool on the paper. Serve with extra raspberries, if liked.