RG, for a deluxe version I would halve the tomatoes and peppers and scoop out seeds and pith, then roast them in the oven with peeled quartered onions and maybe some (unpeeled)garlic - if your baby is a bit older - and olive oil until the veggies are all soft. Lemon juice gives it a bit of a lift. I'm never quite sure about timings and temperatures, just trial and error, maybe put in at medium temp and check after 20 mins or so. Soften pepper skins by putting peppers in a plastic bag so the steam loosens them and then cool and peel. (you can carry on roasting onions as you do the peppers.)Tomato skins should come loose as you roast. Peel roasted garlic tasting it to check it has not got burnt and bitter. Blend it all together. Roasted carrot is also really nice in this.
Otherwise I would just finely chop all the veggies and discard seeds, then fry onions and maybe chopped garlic - then add peppers and tomatoes and simmer with some mixed herbs/parsley/basil/thyme until nice and soft, then blend. If you freeze it you can add chicken, courgettes or other things to make it more interesting later on.
If you want to remove the skins of the tomatoes prior to frying then drop them in boiling water for a few seconds to loosen them, then peel when cool enough. I never bothered peeling tomatoes - found the skins just went straight through my son with no ill effects but the tomatoes were quite acidic so too much could give him a bit of a red bum. I must say I use tins of tomatoes more often though.
Hope this isn't too muddly, baby is on sort of a "timer" before she kicks off. Happy cooking!
That makes my favourite food of all time...fry onion (chopped up small) in olive oil, add chopped peppers, add tomatoes, cook until soft, add tons of basil, if you have it, and perhaps some oregano - there you have it.
If for young baby, sorry I was thinking of DD - blend it once cooked to make it smooth, I love it like that too! And add some water to soften flavour if too strong. My DD loved strong flavours from the outset.