Slice the onion thinly and soak in water. Drain the water.
Mix all ingredients for the marinating sauce in a plastic bag and mix well. Rub with your hands to mix quickly.
Chop the cured ham into bite-sized pieces, and slice the lemon into thin slices. Chop the lemon slices in half (or fourths).
Add chopped ingredients into the bag and rub slightly. Chill in the fridge for 20 to 30 minutes to marinate.
Here's a variation with red onions. They don't taste too piquant and look quite pretty.
Story Behind this Recipe
I love marinated salmon, so I tried to make it with cured ham.
Don't use too much salt in the marinade because the cured ham is already salty. You can also use thinly sliced roast ham instead because it won't be salty like the cured ham. Make sure to use lots of salt.