Heat oven to 200C/fan 180C/gas 6.
Toss the potatoes with 2 tsp oil and some
seasoning. Tip onto a large baking tray,
then roast for 20 mins, stirring halfway,
until crisp, golden and cooked through.
Meanwhile, put eggs in a small pan
of water, bring to the boil, then simmer
for 8-10 mins, depending on how you
like them cooked. Plunge into a bowl of
cold water to cool for a few mins. Peel
away the shells, then cut into halves.
In a large salad bowl, whisk together
the remaining oil, red wine vinegar,
capers and chopped tomatoes. Season,
tip in the onion, spinach, tuna and
potatoes, then gently toss together. Top
with the eggs, then serve straight away.