Combine the vine-ripened tomatoes, sugar, vinegar and fennel seed in a medium saucepan. Bring to a boil; then reduce heat to medium. Continue cooking until all excess water is cooked out and the preserves become glossy. Fold in the cherry tomatoes; reduce heat to medium low. Stir frequently but gently, so as to not crush the halved cherry tomatoes. When the jam holds a line on a cold plate, it is ready.

Remove from heat and ladle hot jam into a jar, leaving ¼-inch headspace. Using a non-metallic utensil, remove air bubbles and adjust headspace by adding more jam. Wipe jar rim to remove any food residue. Centre hot sealing disc on clean jar rim. Screw band down until resistance is met; then increase to fingertip tight. Return filled jar to rack in canner. Repeat for remaining jam. When canner is filled, ensure that water covers all jars by at least one inch. Cover canner and bring water to full, rolling boil before starting to count processing time. Boil for 10 minutes. Turn off stove, remove canner lid and wait five minutes.

Remove jars without tilting; place them upright on a protected work surface. Cool upright, undisturbed for 24 hours. Do not retighten screw bands. After cooling, check jar seals. Sealed lids curve downward and do not move when pressed. Remove screw bands; wip and dry bands and jars. Store screw bands separately or replace loosely on jars. Label and store jars in a cool, dark place. For best quality, use within one year.

Yields about two litres or eight 250-millilitre jars.