A tomato plant is roughly ~40lbs/sqft/year (hydroponic... at 40W/sqft). That's a bit higher than the 80kg/m^2 estimate, but I don't have the wattage requirements for the lower yield. But, assuming it is linear, about 20Wh/g-tomato.

And then, from a climate impact standpoint... The marginal CO2 emissions factor in the Netherlands is pretty high at ~0.6kg/kWh, so ~2kg-CO2 for every (~6oz) tomato. That is about 200-300x higher than the CO2 from trucking (refrigerated) tomatoes from Spain to Netherlands (~30-40kg-CO2/ton-tomato/1000 miles ~= 7g-CO2/tomato).

The local ecological (water+fertilizer+pesticide) impact is probably higher in Spain (vs the greenhouse construction and land use in the Netherlands), though it is hard to know how much to trade that off.