Slice the tomatoes in half (or quarters if larger) and lay out on a lined baking tray. Sprinkle with sea salt and cover with a clean cloth. Place in the fridge overnight to draw out excess moisture in the tomatoes.
If you used a large amount of salt, rinse the next day and drain well.
Pop your washed jars in the oven to sterilise
Meanwhile, to prepare the brine, put the vinegar, water and sugar in a saucepan and bring to a soft boil until the sugar is completely dissolved. If you are making the curry brine, add the curry powder to the brine while it is on the stove top to dissolve. If you rinsed the salt from the tomatoes, add a small pinch now.
With super clean hands, place your pickling spices (excluding the curry powder which should already be in your brine) in your warm, sterilised pickling jars.
Pack the tomatoes in to your jar - you want to pack as many as you can without squashing them. Aim to fill the jars to just below the rim.
Carefully pour over the hot brine making sure the tomatoes are completely submerged. You may need to shuffle some of the tomatoes and add more but make sure there is around 1 cm "headspace" between the brine and the lid.
Slide a chopstick around the jar to remove any air bubbles in the brine.
Seal the jar with a sterilised lid.
Heat processing prevents bacteria from growing within the jar and helps to create pressure within your jar. To heat process, place a folded tea towel in the bottom of a large, deep pot. Place the jar or jars in the pot on top of the cloth (make sure there is space between) and fill with water (as close to the same temperature as your jars as you can) to three-quarter full.
Bring the water to a boil for 10-15 minutes for smaller jars (500ml and less) and 20 minutes for larger jars. The lids will convex during this process.
Carefully, using either canning tongs or oven mitts, remove the jars and set on a tea towel on your counter overnight.
If you are concerned that your jars didn't seal properly, store in a fridge to pickle for six weeks. The longer you allow the tomatoes to pickle the better. If the you are happy with your jar seals, store in a cool dark place to pickle for 6 weeks or more.