Spotted in Southern Ontario, not far from Toronto. Medium tree – between 15-20 feet, wider than tall, compact. Very much resembled an apple tree, even the fruit had a similar texture and opacity to apples – but the blush-pink fruit grew in conjoined groups of 2-5 (mostly 2 or 3) almost like a bean pod. Could it be some weird form of crab apple?
Thank you for contacting the Toronto Master Gardeners. The drawing and description of multiple, conjoined fruits you provided is certainly unusual. It sounds like you have already done a fairly extensive search and a definitive identification may be elusive. There are a few possibilities to consider.
Firstly, you could be witnessing the phenomenon of multiple conjoined fruit. This can happen on many kinds of fruit trees under certain conditions, particularly stone fruits like peaches, cherries and plums. Very hot and dry conditions in the previous growing season disturb bud development and can lead to double fruiting the following year. You can read more about double or conjoined fruits here.
It is also possible that you saw large seed pods of some kind. Trees like the Kentucky Coffee tree have large seed pods but they are typically flat and leathery in appearance. The seed pods of some magnolias such as M. stellata may appear like multiple fruits.
Fig trees can be grown in Southern Ontario with special care and the fruits can resemble your drawing, although not conjoined. The fruits of the Sycamore Fig (Fiscus sycomorus – also called fig mulberry) cascade down from the trunk and branches. It is not clear whether this species of fig can be successfully grown in Ontario.
Finally, it is possible that you were looking at a Pawpaw tree (Asimina triloba). These trees are unique to the Carolinian forest and southwestern Ontario is the northernmost region for this species. However, the fruits are typically yellow-green and not the colour you described. The leaves are elongated and smooth. Pawpaw fruit do grow in clusters. More information about the Pawpaw tree can be found here, and here.
I hope this information is helpful to your quest.