1. Smaller oceans.
Reverse the ratio of land to water. 75% land, 25% water will mean there is no continuous path for water to flow from equator to poles. This results in much lower heat transport. Consider the temperature difference between Hudson Bay and Scotland, both at the same latitude. Look at the climate of Rome compared to New York, aslo at the same latitude. This would create a climate with smaller climate zones. Should get faster evolution (more isolated populations) with overall greater diversity.
2. Less water in the air.
Water is a significant green house gas. And water has a huge latent heat between liquid and vapour phases.
3. Smaller green house effect.
#2 does some of this, but lower CO2 would do it too. During the Earth's warm periods, the equator was not much warmer than today, but palm trees grew up to the Arctic Ocean.
4. Faster rotation -- shorter day.
Stronger coriolis effect. This would make for a larger number of Hadley cells between equator and pole, requiring more heat exchange cycles for energy to move from equator to pole
5. Dispersed land -- more islands, fewer continents
Even if you don't go with more land relative to water, break it up more. With more obstacles and edges, there will be more friction on ocean currents.
6. Shallower seas.
More friction again. Less heat storage.
7. More mountains.
Or just run more ranges east-west. Mountains contain water movement by wringing out the moisture. At present the Americas span the equator. Turn the continents sideways, at latitude 30, and the mountains would block a lot of water vapour moving away from the equator. This would contain heat at the equator.
8. large continents at the poles.
More continental climate with greater temperature swings on an annual basis. There's a reason that Antarctica is colder than the Arctic.
It would be quite easy to create a world that had such extremes that anything that could live at mid latitudes would perish at the equator from heat.
If this isn't extreme enough, give the planet an eccentric orbit. This may mean that you can only cross the equator at aphelion, when the planet is farther from the sun. Give the planet some tilt too, then for one hemisphere, the orbit and axial tilt induced seasons partially cancel, and for the other hemisphere they reinforce.