I planted a few onions under my 30 rose bushes, one per bush. I have not had aphids on the roses in all of these years now. I leave the onions in the ground, and they multiply like crazy, so pull up some every yr. What I read was they emit a odor or taste to the rose plants and the aphids can't stand the taste of the onion. Myself, I do not know if the tomatoe will absorb the taste of the onion, but then, you may start another flavored food. Also there is a hot pepper spray on the market in garden dept. for bugs, and it is just red hot peppers. You also could make that in a blender, hot peppers and water. I have seen the recipe posted somewhere.
Darlene

My grandfather swore by banana peels. He'd toss them on the soil under his tomatoes and roses as a cure for aphids. He said aphids didn't like a certain gas that's released when the peels rot. I've tried it and it does seem to work. But then you can't harvest rotted banana peels later. ;^)

good gardening to you