How to add a little "je ne sais quoi" to tomato-based (saucy) dishes

[QuimReaper]

I read a tip here recently to add a splash of white wine vinegar to "white" dishes (like leeky soups etc.) at the end of cooking to give it a little something extra, and it really does work.

Is there an equivalent for tomato-based dishes? In the last couple of weeks I've made a beef stew and a sausage one in my slow cooker and they've been "fine" but somehow lacking in depth. Maybe a bit acidic, I'm not sure. I find the same thing with ratatouilles, although I tend to be heavy-handed with herbs in that so it's not so much of a problem. Is there a similar hack for tomatoey dishes? Maybe Lea & Perrins?

And yes a extra knob of butter at the end and a frozen Parmesan nub stick in if you have one for good measure.

I'd just chuck leftover anchovies in a small tupperware, is that what you do Dippy? Great idea!

YY to cinnamon. And a splash of lemon juice.

A small amount of milk added before you start to reduce is pretty undetectable and gives a more rounded flavour, somehow.

Stock cube (preferably ham but veg one works too)