Yes, TOMATILLO is a Scrabble word!

Letter values in Scrabble US: T 1, O 1, M 3, A 1, T 1, I 1, L 1, L 1, O 1.

Is it a valid word?

TOMATILLO is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

Mexican annual naturalized in eastern North America having yellow to purple edible fruit resembling small tomatoes
annual of Mexico and southern United States having edible purplish viscid fruit resembling small tomatoes
small edible yellow to purple tomato-like fruit enclosed in a bladderlike husk

Also: purple ground cherry, physalis philadelphica, mexican husk tomato, physalis ixocarpa, husk tomato.

Not playable in Scrabble US: MILTOMATE, JAMBERRY.