Place the chopped onion in a small bowl and cover with cold water. Soak for 5 minutes while you prep everything else. Drain well and pat dry.
In a small bowl, whisk together the olive oil, balsamic vinegar, lemon juice, salt, pepper, and berbere until emulsified.
In a large bowl, combine the tomatoes, drained onion, and jalapeño. Pour the dressing over and toss gently.
Cover and refrigerate for at least 30 minutes. The salad will release juice as it sits — this is correct.
Drain the accumulated juice into a small bowl and set aside (see Notes). Toss once more and serve chilled.
Notes
If you're looking for a high quality berbere, I highly recommend this one. It's what I use when I don't grind my own, and it's as close to the authentic versions you get in the spice markets of Addis.
The reserved juice is worth keeping. Drink it straight, mix into a vinaigrette, spoon over rice, or add to a Bloody Mary.
Timatim kurt refers to the chunky ½-inch cut — don't fine-dice or the salad turns mushy.
Roma tomatoes work as well as plum. Ripe tomatoes are non-negotiable.
Best within a few hours of making. Refrigerate leftovers up to 1 day.