- Place onion, garlic, basil leaves, salt, and pepper in a Mason jar. Mix well.
- Add vinegar and marinate for 15 minutes. Add mustard and oil, secure lid and shake well. Set aside.
- Fill a medium saucepan with cold water. Add salt, and cook potatoes for 12 to 15 minutes depending on their size. Remove cooked potatoes with a skimmer and cut them in half. Drizzle with a bit of vinaigrette and set aside.
- Bring water back to a boil and cook the beans for about 4 minutes. Strain and immerse in cold water for 1 minute to stop the cooking process.
- In a large bowl, add the tomatoes, olives, potatoes, beans and sliced red onion (if desired). Drizzle with as much vinaigrette as needed and mix gently. Taste and adjust seasoning. Set aside.
- Generously salt tuna steaks on both sides, then sprinkle with ground pepper.
- Heat a skillet on high. Add a drizzle of olive oil and sear steaks for 2 or 3 minutes on both sides.
- Remove from heat and allow to sit for 4 minutes.
- Serve the salad onto four plates. Top each plate with a tuna steak and several hardboiled egg quarters. Drizzle a little vinaigrette on top if desired.
Cooking hardboiled eggs
Put the eggs in a medium-size saucepan, cover with cold water and add salt. Bring to a boil, turn off the heat, cover and let sit for 10 minutes. Remove the eggs, run them under cold water for a few minutes then peel them under cold water.
Cook more beans or potatoes and use the rest of the vinaigrette to make salad topped with canned salmon or sardines for lunch.