Place two oven racks to divide the oven space into thirds. Pre-heat oven to 225°F/110C/Gas Mark ¼.
Line 2 baking sheets with parchment paper. Draw as many heart-shaped traces as your baking sheet can fit using a pencil and a heart-shaped cookie cutter. Turn the parchment pieces upside down to prevent pencil from getting into your meringue.
In a large bowl, beat egg whites with cider vinegar to soft peaks. Beat in sugar in small batches while mixing on high till stiff, glossy and smooth. The last step is to beat in the food coloring and raspberry extract.
Transfer the raw meringue into the bag. Follow the heart-shaped traces you made to pipe the outlines, then fill them carefully.
Bake for 2 hours till firm. Turn the oven off, but leave the baking sheets inside. Let sit for 2 hours or overnight till completely dry and crisp.
Remove meringue hearts from the parchment; transfer to a plate. Before serving, dust with confectioner’s sugar.