Instructions

1. Pick tomatoes that are fully ripe but still firm enough to slice without collapsing. A soft one turns to pulp under the knife and the pulp welds itself to the tray.
2. Cut out the core and the pale hard shoulder around the stem. That part stays tough no matter how long the run is, and it is the piece people bite into and blame the method for.
3. Slice across the fruit at about 6 mm. Cutting across leaves the seed chambers open so the jelly and the seeds can dry, where a slice cut down through the stem traps them in a closed pocket.
4. Lay the rounds cut side up on the trays without overlapping, and shake off any loose seeds first. Loose seeds fall through the mesh and burn onto the tray below.
5. Dry for 8 hours at 57 °C. Expect the slices to shrink to about a quarter of their size and the colour to go from red to a dark brick.
6. For slices you will rehydrate, stop while they are leathery and pliable with no bead of juice when you tear one. For powder, push on until a slice cracks like a chip, because anything soft will gum up the grinder.
7. Cool them on a rack for an hour, then condition the leathery ones: a week in a loosely closed jar, shaken each day, and back on the trays if you see condensation on the glass.
8. Store them in an airtight jar in a dark cupboard for a year, or grind them into powder and use that within three months. The powder has far more surface exposed to the air and it loses its smell long before the slices do.